Viviparity of Amphipholis.

The fact that Amphipholis squamata, together with some other echinoderms, is viviparous raises an important question which appears almost to have escaped notice hitherto. It is a belief very common among embryological workers, and one frequently referred to in current papers (e.g., Just, 1928), that the coelomic fluids of echinoderms exert a strong toxic or inhibitory effect upon the ova. This, it is stated, is the mechanism by which embryos are prevented from developing within the body of the parent. In descriptions of methods of artificial fertilisation of echinoderm eggs it is stated with emphasis that eggs will not develop when excised from the gonad and gonoducts unless all traces of coelomic fluids are carefully excluded. The point arises here of how it is possible for embryos of Amphipholis squamata to develop within the thin-walled bursae of the parents; for it is improbable that traces of coelomic fluids would not diffuse through the bursal wall when it becomes thin and stretched by the growing embryo; and, in any case, as shown below, there are strong reasons for believing that a fluid is actually secreted by the bursal wall on to the embryo.

Furthermore, a number of cases have been recorded during the last forty years in which viviparity has occurred in species normally oviparous—and in which, according to the theory of “coelomic toxins,” internal development is not possible. It is a notable fact that in these cases of viviparous habit in oviparous forms, the condition is associated with, and can be fairly certainly regarded as caused by, a hermaphrodite state of the reproductive organs. The following records are known to me of hermaphroditism occurring abnormally in echinoderms: Asterina gibbosa (Cuenot, 1898); Asterina batheri (Ohshima, 1929); Asterias glacialis (Delage, 1902, and Buchner, 1911); Sphaerechinus granularis (Viguier, 1900); Strongylocentrotus droebachiensis (Gadd, 1907); Paracentrotus (or Strongylocentrotus) lividus (Herlant, 1918; Gray, 1921; Drzewina and Bohn, 1924; Paspaleff, 1927); Arbacia pustulosa (Gray, 1921); Arbacia sp. (Heilbrunn, 1929); Echinocardium cordatum (Paspaleff, 1927; Moore, 1935); and Echinus esculentus (Moore, 1932). The tendency to develop hermaphroditism, as shown by the above list, is thus not confined to one or two examples. Of the instances given above, the hermaphroditism is described as functional in six cases. Thus, in the specimen of Echinocardium cordatum examined by Moore (1935) there were larvae and eggs in the gonoducts, eggs having been fertilised by the animal's own spermatozoa.

It is thus quite clear that the supposed inability of echinoderm eggs to develop in proximity to the body fluids does not agree with the facts as observed in nature, and the belief rests entirely upon some data obtained from artificial fertilisations made in the laboratory. All the facts brought together above are in support of a claim made by Bogucki (1930), who also challenged the truth of the theory. He, however, approached the question from the results of experimental cultures of excised echinoderm eggs, artificially fertilised. Bogucki claimed that inhibition of development was not caused by the body fluids of the parent, but happened only if the gut was