ARGOXAUTA ARGO AND THE IIECTOCOTYLI. 7-3 



of perfect spermatozoa. In this case a special investment is fre- 

 quently not to be discovered, as Kolliker and Von Siebold (VergL 

 Anat. p. 411) state; in a few instances, however, the greater 

 part of the thread was surrounded by a distinct structureless 

 membrane. 



Its existence was clear in places where it stretched over gaps 

 in the contents, or where it was quite empty, and also in places 

 where it was torn, and the masses of spermatozoa had swelled 

 up and made their way out. Whether this investment is a true 

 membrane which subsequently disappears, or whether more 

 probably it is rather an accidentally deposited homogeneous mass, 

 I will not attempt to decide ; only it is to be noted that this in- 

 vestment was not to be found in a few other portions of the same 

 seminal cylinder. 



The one end of this filiform seminal mass is connected with 

 the bulb which forms the commencement of the ductus deferens 

 (ductus ejaculatorius, V. Siebold) described by Kolliker. One 

 part of it lies coiled up with the seminal cylinder in the checkered 

 vesicle, the other part stretches on into the penis. 



This peculiar ductus deferens* appears to consist of a sub- 

 stance essentially identical throughout, but varying very greatly 

 in consistence and form in different localities. It is a yellowish 

 or colourless^ sometimes tough, sometimes more brittle, but 

 elastic mass, which frequently, e. g. in the interior of the bulb, 

 is tolerably soft, but at other places is of almost horny hard- 

 ness and friability. Histologically, it appears sometimes struc- 

 tureless, sometimes marked very beautifully with parallel stria- 

 tions. The striae are either immeasurably close or 0'004 (fre- 

 quently 0'001-'002) of a line apart, and exhibit transitions from 

 the most extreme delicacy to very marked lines. 



They have the greatest similarity with those which we see in 

 the wall of the Echinococcus vesicles. The structureless mass 

 appears to pass into more slightly or more strongly marked 

 layers which determine the partly longitudinal, partly transverse 

 striation. This often takes on very strange forms when the 

 parts are torn, doubtless in consequence of the folding and tear- 



* I retain this term, although the part does not seem to he quite analogous 

 to the organ so named in H, Aryonauta. 



