278 On the Interpretation o/Poljparium ambulans, Korotneff. 



probably deep-sea form of Actinia by external influences, 

 such as the bite of a fish or the nip of a crab's claw, which 

 has been brought up from its original locality into shallow 

 water, where it finds an abundance of food in the well-popu- 

 lated sea, and can obtain therefrom by inception through the 

 buccal cones such plentiful nutriment that it not only brings 

 the original wounded surface to cicatrize, but grows on more 

 and more into a band-like shape. In this case the peculia- 

 rities of the transverse musculature and the locomotive appa- 

 ratus may have been derived from the original form, which is 

 still unknown to us. For the tripartition present in the foot 

 I have no interpretation. 



Such an explanation, as will be seen, approaches in a cer- 

 tain way to the interpretation which Giinther * has given of 

 the Leptocephalidge. Accidental but constantly recurring 

 circumstances carry away eggs or young brood of fishes 

 which spawn in the littoral waters into pelagic regions or 

 currents, and here, under unusual conditions of existence, 

 ensues the development of these peculiar forms of fishes, 

 which, by their possession of a gelatinous mass around the 

 vertebral column, perhaps differ as much from other fishes as 

 Polyparium amhulans from normally constructed Malaco- 

 dermata. The paranomally developed Leptocephalidge are 

 incapable of reproduction as such ; only the constant recur- 

 rence of similar conditions calls these creatures into being. 



Perhaps also those animals which have recently been 

 known exclusively as inmates of aquaria are to be interpreted 

 in the same way. I refer to Ti'ichoplax adhcerensj F. E. 

 Schulze t, and perhaps the singular Ctenodrilus monostylos^ 

 Zeppelin j, may also be placed in this category. If these are 

 also paranomally developed animals, they differ from the 

 Ilelmichthyidse by the possession of the power of reproduc- 

 tion ; but so far as is yet known they are capable only of 

 asexual propagation ; the starting-point of Trichoplax is 

 indeed quite unknown, but for Ctenodrilus monostytos it is 

 not far to seek. We might also refer to Protohydra Leuck- 

 art'i, R. Gr., and suppose that this form, in which we only 

 know asexual reproduction, becomes specially developed in its 

 habitat, the oyster-park of Ostend, under circumstances which 

 approach those of an aquarium, if it were not that E,einhard § 

 mentions the occurrence of this animal in the Black Sea, but 

 without any indication of the special circumstances. I adduce 



* ' Introduction to tlie Study of Fishes ' (1880), p. 181. 

 t Zool. Anzeiger, Jahrg. vi. (1883), p. 92. 

 t Zeitsehr. fiir wiss. Zool. Bd. xxxix. p. 6] 5. 

 § Zool. Anzeiger, Jahrg. vi. (1881), p. 692. 



