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Of sixty-seven adult female Periplaneta americana (L.) isolated when less than 8 h old and kept without food at 25-30°C in LD 12:12, only six produced oothecae during 25-35 days. Growth of the basal oocytes was retarded, and maximal oocyte volume, only one-third of that in fed virgins, was achieved after about 12 days. By day 14, 60% of the basal oocytes were being resorbed in the starved females, and corpora lutea were usually all that remained beyond day 20. Oocyte growth was potentiated in starved, virgin females by severing either of the two nervi corporis allati 1 (NCA l), and oothecae were then produced in 45-80% of cases. Sham-operated controls oviposited in fewer than 27% of the trials. Because oocyte maturation was prevented by extirpating both corpora allata (CA), but not when the glands were replaced, and because the juvenile hormone analogue, ZR 5 15, was highly effective in causing the starved cockroaches to produce oothecae, the starvation-induced reproductive failure probably reflects diminished hormone production by the CA. The most likely consequence of severing NCA 1 is de-repression of juvenile hormone production. The directness of the neural influence was shown by removing the one denervated CA, in which case stimulation of oogenesis was minimal even though the contralateral innervated gland was present. The incidence of ootheca production was not enhanced by transecting the NCA 2, which suggests that the CA of starved cockroaches are not inhibited via this pathway.

Retrograde diffusion and precipitation of Co2+ reveals in the ipsilateral pars lateralis (PL) and contralateral pars intercerebralis (PI) of the brain neurons that enter the corpus cardiacum (CC), and, possibly, the corpus allatum (CA) on each side. The PL group consists of 29.6 +/- 8.4 somata that fill. Of these, 5.6 +/- 0.6 exceed 25 micrometer in diameter, 14.3 +/- 2.7 range from 15--25 micrometer, and 9.6 +/- 7.6 are smaller than 15 micrometer. After CoCl2 was applied to the right CC-CA of two males, 239 and 265 somata in the left PI stained. Except for 16 ranging from 30--45 micrometers and chiefly located anteriorly, a majority of these somata measured 10--25 micrometer. The only somata revealed by staining whole brains with the performic acid-resorcin fuchsin method are neurosecretory cells 10--20 micrometer in diameter located within the PI. In starved adult males there are 92.4 +/- 8.1 on the right, and 93.2 +/- 6.9 on the left. The largest somata in the PL group contain numerous granules that stain with paraldehyde fuchsin. These somata also fill with Co2+, and belong to neurosecretory cells that extend into the CC-CA. The cerebral distribution of branches from the PL group, and the relationship of these to the corpora pedunculata, central body, and arborizations from the PI decussation are described.

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A growing interest in the neuroglial elements of the vertebrate nervous system is evidenced by a steadily accumulating literature, and by the appearance of two recent monographs (Glees, '55; Windle, '58). These efforts are justified by the supposition that neuroglia and its equivalent in the peripheral nervous system (satellite and Schwann cells) execute a role in the economy of nervous tissue which is considerably more dynamic than that of mechanical support. Thus, these non-nervous elements are presumed to participate in the formation and maintenance of myelin, in nerve regeneration, in the functioning of the blood-brain barrier, and probably in electrophysiological phenomena related to nervous activity.Relatively little is known about the structure of invertebrate neuroglia; still less about its histochemistry. As a consequence those unifying concepts so frequently provided by the comparative approach are lacking. An understanding of the structure of invertebrate neuroglia is also important in its own right, constituting a prerequisite to investigations of its functional significance. The present study on certain features of insect glia is a contribution toward this end. MATERIALS AND METHODSThe majority of observations were made on the nervous systems of adults of the cockroaches Periplaneta americana (L.) and Leucophaea maderae Fab. First instar nymphs of these two species, as well as adults of the milkweed bug, OncopeZtus fasciatus (Dallas), and the Bermuda land crab, Gecarcinus lateralis (F.), were examined in order to clarify certain points. The animals were usually killed and fixed as described previously (Pipa et al., '59). Alcoholic Bouin's, aqueous Bouin's, Lillie's acetic-alcohol-formalin (AAF; Lillie, '54) , Regaud's followed by postchromation, Helly's, and 10% formalin were the fixatives most commonly employed. With few exceptions the nerve cords were dehydrated with normal butyl alcohol, vacuum infiltrated with tissuemat (60-63°C) and sectioned at 5-7 p.Histological staining techniques Histological features were revealed by examining the preparations stained with cresyl violet (pH 3.5); toluidine blue (Lillie, '54); Mallory's triple stain; Gomori's aldehyde-fuchsin following the procedure of Halmi ('52); Gomori's chrome alumhematoxylin (GCAH; Gomori, '41) ; muver and Barrera's copper phthalocyanin method (CPM; Pearse, '60); Einarson's gallocyanin (pH 1.6; Pearse, '60); and van Gieson's picrofuchsin. Histochemical techniques Polysaccharides.The periodic acidSchiff (PAS) reaction was employed on diastase-digested sections in a manner essentially similar to that described previously (Pipa and Cook, '58). Sections which had not been oxidized with periodic acid served as controls. The extent to which aldehyde groups contributed to any positive reaction observed was determined by employing the aniline-acetic acid blockading procedure of Lillie and Glenner ('57). The PAS reaction was either negative or greatly reduced by eliminating periodic acid oxidation, or by blockading.To decide whether structural ...

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