Morphogenesis in Limnaea stagnalis and its disturbance by lithium

The nature and origin of the cortical morphogenetic field in Limnaea

“…In some earlier papers (Raven, 1958a(Raven, , 1958b(Raven, , and 1961) I have put forward the view that the pattern of the cortical field is "imprinted" upon the egg during oogenesis by the surrounding structures and have adduced circumstantial evidence in support of such a view. This evidence mainly concerned the probability that the main directions of the field are established in conformity with the position of the egg in the gonad.…”

“…As the future spatial pattern of the embryo is to a large extent dependent on the "blueprint information" in the cortex of the egg (cf. Raven, 1958a), it appears that the prodromes of this pattern are transmitted from the parent to the offspring through this channel.…”

“…The results of our experiments on treatment of the eggs with lithium chloride (Raven, 1942)) in which we obtained a roughly continuous series of cyclocephalic malformations, ranging from a slight mediad displacement of the eyes and tentacles, via synophthalmia, cyclopia, anophthalmia, to complete acephaly of the embryos, were interpreted by the assumption that the cortical field in Limnaea has the character of a gradient field with high point at the animal pole (Raven, 1949(Raven, , 1952. Lithium, by depressing the apex of the gradient field, was supposed to suppress the differentiation of the most animal structures, the ciliary cells of the so-called apical plate.…”

“…Furthermore, an attempt has been made to throw some light on the problem of the way in which the presumed cortical mosaic comes into being. In previous papers (Raven, 1958a(Raven, , 1961 I have put forward the view that the structure of the cortical field reflects the mutual positions of the elements surrounding the egg cell in the gonad. The observations dealt with in this paper give further support to this supposition.…”

The action and interaction of calcium and alkali chlorides on eggs of Limnaea stagnalis and their chemical interpretation

“…dlong this line it is impossible to come to a conclusion on the site of action of the ions, but it would be of importance if we could only discriminate between nuclear, cytoplasmic or surface action of the ions. From the studies of morphogenesis following treatment of eggs with LiCl, cortical field theories have emerged which state that development is governed by a graded distribution of cortical factors [5]. In this reasoning the action of ions is assumed to be localized at the cell surface [3, 4, 81.…”