AND XOOGEOGRAPIIY OF IXDIAN OLIGOCHyKTA. 115 



usually (perhaps at a later stage) shows a smaller ring-like aggre- 

 gate in the centre (text-figs. 3 & 4). These characters distinguish 

 the young sexual cells from the ordinary peritoneal cells and 

 from the cells of the proliferations in the budding zones; in 

 these the nuclei are on an average ^'S to 5 /a in diameter, and 

 the chromatin has no characteristic arrangement. 



(2) The next stage, or young morula, consists of an ovoid 

 aggregate of cells, which appear to be lil^tle else than naked 

 nuclei (text-fig. 5) ; these are still of about the same size, with 

 the clear circle and central aggregate of chromatin. 



(3) The cells become peripheral, leaving a granular mass in the 

 middle of the morula ; cell boundaries are not distinguishable, 

 but the peripheral region of nuclei is raarked off from the central 

 granular mass (text-fig. 6). The characteristic arrangement of 

 the chromatin disappears. 



(4) The moruUiD, attached up to this stage, may now become 

 free. 



General Remdrks. 



Chcetogasiei' orientalis appears to be the only Oiigochsete in 

 which a difi:use production of sexual cells, similar to that of the 

 Polychseta, has hitherto been described. It is possible, however, 

 that the phenomenon may occur in other species of the genus, 

 though the statements of previous authors (in particular Vej- 

 dovsky, cf. ant.) seem at first sight to negative this. 



The testes of G. diapJianus are figured by Vejilovsky (pi. v. 

 fig. 4) as rather loose masses of cells some little distance behind 

 the septum, and are said in the text to arise on the first pair of 

 nerves given ofi^ from the ventral nerve cord. The cells are 

 loosely aggregated, and not bounded by a peritoneal membrar^e ; 

 they grow rapidly to four times their original size, become free 

 in the body-ca.vity, and then soon attach themselves to the various 

 organs and go through their further development — for example, 

 on the ventral nerve cord, or on the alinientary caual. The 

 later stages again become free. The original testes quickly 

 disappear. 



It will be noted that. the mass of cells which Vejdovsk}^ calls 

 the testes are not in the normal posjtion of these organs ; and it 

 seems possiblp that they are only two am.ong the numerous 

 groups of sexual cells which ai^e, accordiiig to my observations on 

 G. o'z'eJi^rtZis, scattered about the body. Probably also, in view 

 of the I'esults of my sections of G. orientalis., the developing male, 

 cells which Yejdovsky describes as having become attached to 

 various organs really originated from their peritoneal covering, 

 in the same way that they originate, according to the above 

 descriptions, from strands, from the body-wall, and from tlie 

 proliferating tissue of the budding, zones. 



In the Polychaeta the genital organs are as a rule not strictly 

 localized ; the gonads are proliferations of peritoneal cells which 

 originate on the parietes, on the blood-vessels, or on the alimentaiy 



