242 ENTEROPNEUSTA FROM THE SOUTH PACIFIC, 



I have observed, in every case, in the normal nucleoli of the germinal vesicles of the mature 

 ova of Pt. ruficollie n. sp. (PI. XXX. Fig. 34). 



The number of eosinophile globules whose chemical nature is unknown is alarmingly on 

 the increase. 



If the interpretation which I have suggested at all approaches the truth the globules 

 now under consideration would be composed of a substance allied to pyrenin. It must be 

 added that I have made no observations on the processes of maturation of the germ-cells 

 themselves. This is a subject which presents great difficulties and probably necessitates the 

 employment of a special and elaborate technique. 



Gexito-hepatic Transitu >n. 



The genital pleurae with their contained gonads encroach for a considerable distance 

 upon the hepatic region. The first few hepatic diverticula are internal and do not cause 

 elevations of the integument: they are characterised by their much elongated epithelium 

 consisting of closely packed cells with basal nuclei in an approximately even layer, and 

 containing peripheral yellowish-brown intracellular granular deposits 1 . 



As they approach the hepatic region the genital pleurae begin to diminish in size 

 and to become more and more dorsal, until at the beginning of the hepatic region they 

 are quite dorso-lateral in origin. They maintain their integrity for some distance, but 

 when the hepatic diverticula commence to cause projections of the integument between 

 the genital pleurae, the latter are, at these successive points, greatly reduced in size, 

 widening out again in the intervals between the saccules. Finally, when the latter become 

 more massive, the genital pleurae are reduced to zero at the level of the saccules and 

 only reappear in the intervals as ridges bounding the interannular depressions between 

 the hepatic lobes (PI. XXIX. Fig. 14). 



The hepatic diverticula of the gut have a very rich blood-supply, the vessels forming 

 a rete mirabile on their walls. 



Ciliated Grooves of Intestine. 



These are longitudinal grooves in the wall of the gut in the hepatic and abdominal 

 regions, which Spengel found to be especially characteristic of the Ptychoderidae. They 

 consist on each side of a narrow tract of richly ciliated epithelium more or less overhung 

 or protected by an epithelial covering-pad developed on the medial side of the groove. 



In Pt. flava they are not simple longitudinal grooves but possess metameric sac- 

 culations corresponding in the hepatic region to the intersaccular valleys (PI. XXIX. Figs. 

 12 — 14). They commence at the extreme anterior end of the hepatic region, in the 

 region of the genito-hepatic transition, and they extend backwards to the posterior end 

 of the abdominal region. In some places the sacculations of the ciliated grooves approach 

 very close to the epidermis, almost touching the basement-membrane of the latter. 



1 The blood in the vessels round the hepatic epithelium is sometimes coloured a bright refringent yellow. 



