38 T. KOMAI: STUDIES OS TWO ABERRANT CTENOPHORES 



eight to each subpharyngeal canal, never exceeding sixteen to the former 

 and ten to the latter. In living specimens, the seminal receptacles may 

 be observed under a low-power lens as a series of minute whitish spots 

 arranged nearly parallel with the series of the testes on its inner side 

 (PI. 2, fig. i; r. s). In C. bocki, most of the specimens obtained during 

 summer or autumn months were found to contain the sperm mass in the 

 seminal receptacles. PI. 5, fig. 6 illustrates a section of an individual 

 of that species in which a nearly complete series of the receptacles 

 occurring along a subtentacular canal have happened to appear, with 

 all their terminal vesicles filled each with a sperm-mass. In C. wiileyi, 

 one very large specimen collected in February 1916 was found to 

 contain a sperm mass in most of the seminal receptacles. In C. mitsu- 

 knrii, I have come across no individual showing the organ in such a 

 state. 



As to the origin of the spermatozoa in the organ, it is without 

 doubt that they have come from the dorsal side of the body by des- 

 cending through the tubular part. But it remains to be shown whether 

 the spermatozoa have originated from another individual, though this is 

 very likely to be the case. It is also problematical how and where the 

 spermatozoa in the organ meet the eggs, but probably they make their 

 way through the tissues intervening and reach and fertilize the eggs 

 nearly at the time when the eggs fell into the cavity of the canal. 

 The tissues, in fact, appear to be very diffuse and the\' seem to give no 

 great hinderance against the movement of the spermatozoa towards the 

 eggs. 



The question as to which germinal layer of the ctenophore gives 

 rise to sexual cells was discussed much among previous workers. 

 Aside from the writers of older days, Chun and Hertwig expressed both 

 in 1880 opinions entirely conflicting with each other, the former author 

 taking the view of the endodermal origin of the sexual cells and the 

 latter that of the ectodermal origin. Subsequently, the former ('92) 

 undertook a renewed research on the same subject and arrived at a 

 conclusion practically the same as his previous one. This conclusion 

 Chun's was refuted by Samassa ('92), who expressed his opinion in 

 agreement with Hertwig, and in reply to him, Chun, for the third time 

 ('98), insisted on his former opinion. Garbe, a little later ('01), under- 

 took the .same .study and came to a conclusion largely in conformity 

 with Chun's. In addition to the opinions given above, another assuming 

 the mesodermal origin of .sexual cells was introduced by Schneider 



