THE MALAYAN SPECIES OF ONYCHOPHORA. 65 



tliey are iu the twenty-first and twenty- second. They are 

 present in all stages of transformation, from the unmodified 

 nucleus of the mesoderm to that of somewhat enlarged 

 germinal nuclei. At first they are very slightly modified^ 

 and situated among the single row of nuclei found in the 

 splanchnic walls of the somites. As they grow in size they 

 become pushed towards either side, chiefly to the endoder- 

 inal; that is, away from the cavity of the somite, the cells of 

 which arrange themselves in a layer round them (PI. 8, figs. 

 15 a and 15 6). There seems to be no doubt that they 

 originate iu the mesoderm ; and, in conclusion, I must state 

 that I have no hesitation whatever in saying that von Kennel 

 lias made an error of observation in deriving the genital 

 organs from one pair of somites, and that Mr. Sedgwick 

 appears to be wrong in concluding that the germinal nuclei 

 are endo dermal, unless in these respects the species iu 

 question radically differ from the genus Eoperipatus. 



The Formation of the Ovary. — The coelom of the 

 median portion of the four pairs of somites which take 

 part in the formation of the ovary, is not obliterated as in 

 the somites situated in front. From either side the somites 

 approach one another dorsally, and then fuse to form an 

 ovary which, at first, possesses two absolutely independent 

 cavities, and adheres to the ventral wall of the pericardium 

 (PI. 8, figs. 15 a and 15 h, and 16 h and 16 c). Later ou 

 the septum which separates the two cavities of the ovary 

 becomes broken down near the anterior and posterior ends, 

 but is retained in the middle (PI. 8, figs. 17 a and 17 6). 

 As development proceeds the germinal nuclei, which at first 

 were few, increase in number, and give rise to two germinal 

 bands, which occupy the ventral wall of the ovary and almost 

 fill its cavity. The developing ova are surrounded by follicle 

 cells, and are suspended in the body-cavity, in which for 

 want of space they are Avedged against one another (PI. 8, 

 fig. 17 b), an arrangement which should be contrasted with 

 that described by Gaffron in P. edwardsii (3, pi. xxi, figs. 

 9 and 10). 



VOL. 45, PART 1. KEW SERIES. E 



