174 AETHUE WILLEY. 



bahamensis, and the post-branchial region of P. aurantiaca, 

 is the diffuse arrangement of the gonads. They are not in the 

 remotest degree arranged one after the other, in a manner 

 resembling a paired metameric series, as they are more or 

 less in most other Enteropneusta, but they are scattered in the 

 most irregular way in the substance of the genital pleura 

 (cf. figs. 4 and 5). In correspondence with this multiplication 

 of the gonads, Spengel has shown in the above-named three 

 species of Ptychodera, which he had at his disposal to examine 

 by sections, that several gonaducts may be involved in a single 

 transverse section, each gonad having its own duct, opening to 

 the exterior on the inner surface of the genital pleura. This 

 is also the case in Balanoglossus canadensis, Spengel, 

 in which, however, there is a multiple series of gonads, both 

 medial and lateral, of the gill-pores (cf. Spengel, loc. cit., 

 Taf. 17, fig. 22). Spengel states that he has never found 

 gonads mediad of the gill-pores, either in Ptychodera or 

 Schizocardium. 



It has been quite impossible for me, under the circumstances, 

 to prepare a series of sections, and I have had to make the 

 best of hand preparations and dissection. But the diffuse and 

 irregular arrangement of the gonads in P. flava can perhaps 

 be even better realised in in toto preparations than in sections. 



Figs. 4 and 5 represent a few of the gonads in male and 

 female individuals respectively, as seen under a low power in 

 small detached portions of the genital pleura. The gonads, as 

 shown in the figures, have in both sexes the most variable 

 outline. Their appearance naturally varies somewhat with the 

 state of contraction or extension of the animal or portion of 

 the animal. Detached fragments of the genital pleura will 

 creep from under the cover-glass like a Planarian. 



The integument over the testes on the inner face of the 

 genital pleura in P. flava is characterised by patches of dark 

 brown pigment, and on this account it is possible to distinguish 

 the males from the females (fig. 4a). 



The fiemale gonads (fig. 5) contain a variable number of 

 ova, which do not take up the whole volume of the gonads, but 



