CTENOPHORA. 



29 



Abbott {Op. cit. p. 44) says: "As Willey suggests, there is no doubt that Korotneff was describing 



a section through the tentacles The muscular fibres of the tentacle stalk might well be taken for 



longitudinal musles", Abbott has probably himself understood the whole matter; but Willey, who 

 speaks of "the convoluted bundles of muscles" can scarcely have had the right view of it, since his 

 convoluted "muscle bundles" can evidently be nothing but the curled-up tentacle. — The histological 

 structure of the "longitudinal muscles" is also in full accordance with the supposition of their beino- 

 the tentacle; the "nuclei" round the pheriphery of the bundles are the coUoblasts, the "Fasern" the 

 real muscles of the tentacle. What Korotneff regards as the tentacle is only its basal part. 



Herewith I think that the true nature of this remarkable muscular system of Ctcnoplana has 

 been shown; there is then obviously no essential difference in regard to the muscular system between 

 Tjalficlla and Ctcnoplana, or between these forms and the typical Ctenophores. 



While, thus, neither the gastrovascular nor the muscular system of the two forms differs very 

 essentially and not at all so considerably as would appear from the description of Ctcnoplana, the 

 matter seems different with the genital organs. 



The genital organs of Ctcnoplana were not found by Korotneff; but Willey discovered in 

 his specimens of Ctcnoplana Korotneffi the male genital organs, four in number, situated between the 

 subtentacular and the subsagittal costse, at the outer end of the "terminal lobes" of the main gastro- 

 vascular system, before the beginning of the branching peripheral canals, as may be concluded, 

 though Willey does not state this expressly. As points of resemblance with Tjalficlla may be noticed, 

 their being single glands, not series of glands as in typical Cteno- 

 phores; further that their cavities (the "genital coeca" of Willey) are 

 in direct connection with the gastrovascular system; also their position 

 appears to be mainly the same in the two forms. That there are only 

 four genital organs in Ctcnoplana, eight in Tjalficlla, is, of course, a 

 very conspicuous difference; but it is not unparalleled among the 

 Ctenophores; thus in Euclilora rubra (K611.) the genital products are 

 developed only in the subtentacular vessels, while in Euclilora filigcra 

 Chun they are developed in all eight meridional vessels; this conspi- 

 cuous difference is, however, not held by Chun as of more than specific 

 value, and accordingly this difference between Ctcnoplana and Tjal- 

 ficlla cannot be taken to be of very great importance. More remark- 

 able is the statement that in Ctcnoplana the genital organs rejiresent 

 only the testes, a feature quite unparalleled among Ctenophores. 

 Willey suggests (p. 329, Note) that Ctcnoplana may be a protandric 

 hermaphrodite, which might account for his being unable to find the 



female genital organs. I would think this suggestion much more are those of willey. cae. genital 



caecum, d. genital duct, s'— s^ differ- 

 probable than that the animal is unisexual. It would, however, be g„t stao-es of the development of the 



very desirable to have this question examined closely on fresh material; spermatozoa, t. p. tunica propria. 

 I confess that the figures of the genital organs given by Willey, especially Fig. 9 (reproduced here 

 in Fig. 6), do not seem to me very convincing. In fact "the genital coecum" in this figure with its 



Fig. 6. Section through genital organ 

 of Ctcnoplana (reproduced, in '^\i .size, 

 from Willey, PI. 21, fig. 9). The letters 



