STRUCTURE AND DF.VET.OPMENT OF COET,OI'T..\NA. 41 



he regarded them to be testes and called them "folHcules testiculaires ". 

 He has distinguished them from ordinary testes in their smaller sizes 

 and has considered the latter to be composed of two or three of the 

 former, giving them the name of " testicules composes". Certainly, the 

 invaginations in question show a close resemblance to the testes in their 

 general appearance and in the contents they enclose. Nevertheless, the 

 fact that they are not the testes, but function most probably as sperm- 

 receptacles may be clear from the following features they show : — First, 

 the invaginarions are situated right above the ovarial tracts, i. e. on the 

 perradial side of the wall of the subpharyngeal and subtentacular canals, 

 while the testes are found on the interradial side of the same canals — 

 PI. %, fig. I illustrates most unmistakably the relative situation of the 

 invaginations and the testes; they are arranged in two parallel series 

 clearly distinct from each other (Text-fig. ii of Krempf's work, '21 

 seems to represent a young ovary and not a testis, contrary to his 

 explanation). Second, the cavity of those invaginations is frequently 

 quite empty everywhere. Such empty invaginations are found generally 

 in specimens in which both the ovaries and the testes are still immature, 

 and in such invaginations the terminal vesicle shows, as a rule, a clear 

 and definite outline. In specimens with the gonads showing mature 

 eggs and sperms, on the other hand, the invaginations contain a sperm 

 mass almost without exception, and the wall of the terminal vesicle is 

 often vaculated or attenuated, showing distinct signs of degeneration. 

 The third and most convincing fact is that, the contents of the invagina- 

 tions are invariably mature sperms and any immature male element is 

 never met with in them. 



Bodj/ Parenchy-me. 



The body of Coeloplana is much less bulky than that of pelagic 

 ctenophores and contains but a small quantity of the gelatinous tissue. 

 It is however traversed richly by muscle-fibres and pigment cells, so that 

 it looks very different from the same tissue of those ctenophores. The 

 muscle-fibres form nowhere what may be called the bundle; nevertheless, 

 assemblages of fibres running in the same direction are quite common. 

 The mouth, to begin with, is surrounded by the fibres that serve as 

 sphincters. When the animal is dead, the fibres relax and open the 

 mouth widely, so as to expose the pharyngeal folds. The otolithic 

 capsule is also provided with powerful sphincter fibres mentioned already. 



