Summary. From a study of the progressive development of the membranous labyrinth through various larval stages of Xenopus laevis, it is noted that, in essentials, the parts resemble those of the Phaneroglossa. The semicircular canals are separated after the constriction of the auditory vesicle into a pars superior and a pars inferior. The horizontal canal is formed before the anterior vertical, the posterior vertical being the last to appear. This sequence agrees with that of some of the Phaneroglossa (Herter, 1921). The pars inferior produces the sacculus, the pars neglecta, the lagena and the pars basilaris, there being no tegumentum vasculosum as in Rana (Gaupp, 1904). Several membranous structures of somewhat doubtful physiological significance were observed to be associated with the foramen utriculo‐sacculare, the sacculo‐endolymphatic orifice and the aditus partis neglectae. Probably, like the utriculo‐saccular valve of fishes (Pearson, 1936) and the utriculoendolymphatic valve of mammals (Bast, 1928), they serve to maintain an approximately constant pressure of endolymph within the labyrinth. The perilymphatic system appears to differ from the Phaneroglossan condition mainly in having no true ductus reuniens, as a consequence of which the foramen perilymphaticum superius is lacking, and the single perilymphatic foramen is comparable to the foramen perilymphaticum inferius of Rana. An additional tympanal area is to be observed between the anterior part of the pars basilaris and the spatium sacculare. The sacci endolymphatici are paired throughout and are not connected by anterior ascending or ventral processes. Only two pairs of calcareous sacs were observed in the partes spinales. In post‐metamorphic specimens the endolymphatic system could only be traced as far as the region between the fourth and fifth intervertebral foramina. This reduction of the spinal portion of the endolymphatic system, in conjunction with the well‐defined auditory receptor areas in the labyrinth, is not suggestive of primitiveness. Xenopus possesses several structural features which may be regarded more fittingly as neotenic than as primitive. Others, again, may be purely adaptive, and while it is admitted that it may be fallacious to draw conclusions from a few isolated morphological facts, it could be surmised that, anatomically, the membranous labyrinth and its associated endolymphatic and perilymphatic systems indicate a possible reversion of this form from a semi‐terrestrial to an aquatic habitat. At the same time, the same features could equally well be interpreted as an attempt in a purely aquatic form to approach the condition found in semiterrestrial Anura.
The aquatic habit of members of the Pipidae seems to have resulted iii the retent,ion of a number of neoteriic features, and t,hese are evident in the inner ear as well as in other systems of organs.From a comliarative study of the morphological details of the inner ear of adults of Henripipa c w d f t o ; , Hymenochirris curtipes and Xenopus laevis, juvenile Pipa pipa and larval stages of Hem +pa, Xenopus and R a m fuscigula, it appears that the arrangement in Hemipipa is tho Icast. specialized, while the inner ear of Xenopus closely resembles that of amphibious Anura.Attention is drawn to m'itschi 's conclusions (1947-1956) that in larval forms of Ranu and X m o p u s the lungs act as sound receptors, associated with which is the temporary development of certain auxiliary bronchial structures. I n the present observations these structures are interpretod utherv-ise, and no definite conclusions are reached as to their participation in the auditor?; mechanism.Variat,ions in t h o inner ear of tho four species of Pipidae studied appear to strengthen opinions repai,ding the somewhat unsatisfactory classification of the family. Hemipipa and Pipa f d l naturally into the subfamily Pipinae, but the marked differences between Hynzenocftirm and Xc2nopzrs, not only in regard to the inner ear, but also in other anatomical features, suggest, that these two genera should be relegated to separate subfamilies.
SUMMARY. 1. The results of a microscopical study of the nasal cavities of Hemipipa carvalhoi when compared with observations on Pipa, Hymenochirus and Xenopus reveal significant similarities between the latter genus and Hemipipa. 2. It is considered that a recessus olfactorius, similar to that described by Helling (1938) in other Salientia, is present in the Pipidae. The “Nebenhöhle” of Xenopus (Föske, 1934) and the “lateral nasal canal” of Pipa (Bancroft, 1895) cannot, therefore, be homologous with the recessus olfactorius as Helling maintains, and the opinion is expressed that they represent the cavum medium of other forms. 3. The cavum medium (Bancroft's “lateral nasal canal”) consists of anterior and posterior parts, the latter being further subdivided into dorsal‐lateral, ventro‐lateral and medial recesses. 4. The “nasal canal” of Pipa (Bancroft, 1895) is considered to be comparable to the infundibulum of other Salientia. 5. The cavum inferius is divisible into a medial organ of Jacobson and a more lateral part, which Föske (1934) termed the “Mündungszone” of Jacobson's organ, but which herein is compared to the recessus lateralis. 6. The suggestion is made that the thin‐walled, posterior sac, usually regarded as the homologue of the recessus lateralis, may be a diverticulum of the latter, the arrangement of the cavum inferius resembling that of Bombina variegata (Slabbert, 1945). 7. The nasal cavities in the Pipidae are remarkable in that they are mainly lined by sensory epithelium, the presence of which is rather inexplicable unless it be used for olfactory perception when the animal is submerged. 8. Föske's suggestion (1934) that the thin‐walled diverticula of the cavum medium of Xenopus function as accessory pulsating sacs has been examined, but it is concluded that movements of skeletal elements are probably more effective in maintaining the flow of water through the nasal cavities. It is thought that the nasolacrimal duct may be of importance in Xenopus as an inlet for water bathing the sensory epithelium of the cavum medium.
1. Cucumaricola notabilis, a new genus and species of Copepoda, occurs in cysts in the coelom of Cucumaria frauenfeldi Ludwig collected at Sea Point, Blaauwberg Strand and Dalebrook in the Cape Peninsula.2. An account is given of the features of the sexually dimorphic males and females.3. Fertilized eggs and nauplius larvae are also contained in the cysts and, from observations on living material, it has been established that, after escaping from the cysts, the larvae metamorphose within a short period into the copepodid stage. There are two copepodid stages, the first an active swimming form and the second a quiescent phase from which the juvenile parasite develops.4. Although of uncertain systematic position, this parasite seems to be nearly related to the Chondracanthidae. This conclusion is based on the similarity of the trunk appendages of the adult female to those of Acanthochondria as described by Oakley (1930), and also on the general agreement of the ontogeny with that of Acanthochondria cornuta investigated by Heegaard in 1947. It is further suggested that it may be assigned to the key devised by Delamare Deboutteville & Nunes-Ruivo (1955) for certain copepod parasites having some affinity with the Chondracanthidae.
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