154 HRRPOMENIA PLATYPODA. 



specimens examined, a forward section in which the sex products originate, and a 

 posterior division that serves merely as a duct. This latter portion is exceedingly 

 narrow (Plate 8, fig. 3), upwards of twice the bodily diameter in length, is with- 

 out any signs of developing germ cells and contains throughout fully developed 

 sperms. The ova and sperms develop in the customary position, but the former 

 are scant in amount and unusually large, almost completely filling the gland. 



Especially about the periphery each ovum contains imbedded in the yolk 

 large numbers of clear vesicular bodies (Plate 35, fig. 9), approximately 0.0068 

 mm. in diameter with an eccentrically placed darkly staining mass usually super- 

 ficially placed. At first these bodies appeared to be remnants of nutritive cells, 

 possibly modified follicle cells, but subsequent study leads strongly to the con- 

 viction that they are portions of fragmented nuclei. In the early stages of ova 

 development these same bodies occur, but are of extremely small size (Plate 35, 

 fig. 6). Still earlier (Plate 35, fig. 7) it has been possible in several cases to find 

 imbedded in very small ova from one to three cells resembling primordial germ 

 cells, and probably corresponding to follicle cells that are known to occur in a 

 few Solenogastres. These nuclei in a slightly older stage become somewhat 

 larger and stain blue instead of light red or pink. The granules assume the ves- 

 icular appearance characteristic of later stages and slightly later upon the rupture 

 of the nuclear membrane become scattered throughout the egg. Against the 

 belief that these structures are cells may be urged the fact that in their early 

 development they are much smaller than any cell of the body, measuring not more 

 than 0.0008 mm. in diameter, and .secondly there is at no time any sign of a cyto- 

 plasmic mass. These granules correspond closely in size and number to the 

 chromatin bodies, possibly chromosomes, that occur normally in the spermato- 

 cytes. 



In the pericardial cavity the spermatozoa are attached in considerable 

 numbers to the wall especially along the dorsal surface, or at the time of the 

 animal's capture were being swept along in a current passing beneath the heart 

 and outward through the coelomoducts arising from the posterior wall. The 

 dorsal section of each duct (Plate 8, fig. 3) is a simple tube of even calibre through- 

 out, passing downward and forward from the pericardium to unite with the 

 shell gland. Shortly before this union it unites with the duct of the seminal 

 receptacle, which resembles a flask with a long curved neck. This last named 

 organ like the dorsal limb of the coelomoduct is lined with cubical cells possibly 

 ciliated, to which are attached a small number of spermatozoa. 



The shell gland is a globular body and almost totally lacks the cornua 



