ON THE OVIPAROUS SPECIES OF ONYOHOPflORA. 377 



The presence of the ovipositor in Ooperipatus alone 

 amongst Onychophora is in itself strongly indicative of the 

 oviparous habit, while the elaborate and closely similar 

 structure of the egg-shell in both species in which it has been 

 observed also indicates that the habit is constant and normal. 



The Eggs. — The ovarian eggs (0. oviparus), formed pre- 

 sumably from the epithelial cells of the ovarian tubes, range 

 in size from about 0'037 mm. to about 1*4 in diameter. In the 

 youug ovarian egg (fig. 14), as seen in sections stained with 

 borax carmine, the vitelline membrane, if present, is very thin, 

 the cytoplasm uniformly and very finely granular, and the 

 nucleus very large in proportion, to the entire egg. There is a 

 very distinct nuclear membrane, and a single large and remark- 

 ably well-defined spherical nucleolus, with finely granular, 

 darkly-staining contents. The nucleolus is placed excentri- 

 cally, and around it the nucleoplasm stains very lightly, and 

 sometimes at any rate has the appearance of being vacuolated 

 (fig. 14). Outside this light area the nucleoplasm stains fairly 

 darkly with borax carmine. In older ovarian eggs (fig. 15) 

 the vitelline membrane is much thicker and the cell-body has 

 increased in size much more rapidly than the nucleus, owing 

 to the deposition in the former of large quantities of food- 

 yolk, which appears first in the form of minute highly 

 refringent granules thickly scattered through the cytoplasm 

 (tig. 15). In still older ovarian eggs these granules appear 

 to be arranged around spherical globules of some clear trans- 

 parent substance (fig. 16). Some of these globules occupy 

 the interior of irregular polygonal corpuscles slightly larger 

 than themselves (fig. 16). 



In order to study further the structure of the yolk, a 

 quantity was removed from an egg which had passed into 

 the oviduct. This material, which was obtained from a 

 specimen of 0. oviparus which had been preserved for a 

 long time in alcohol, was partly treated with osmic acid, and 

 partly stained with eosin and examined in oil of cloves. The 

 yolk (fig. 17) was found to consist chiefiy of the clear, 

 transparent globules above mentioned, each enclosed in a 



