44 RICHAED EVANS. 



the segmentini>- ovum to an individual which measures from 

 25 to 27 mm. in length, and is coloured almost like the 

 mother. 



The description of the external features of the development 

 will be limited to a number of embryonic stages, which ai'e 

 illustrated in the figures found on PL 5. The youngest 

 embryo successfully taken out of the uterus is illustrated by 

 the first figure on the above-mentioned plate. It seems to 

 represent an early gastrula stage, which is oval in shape and 

 provided with a slit-like blastopore possessing a somewhat 

 irregular outline. The yolk masses situated in the interior 

 are distinctly seen at the sides, but they are not so evident 

 on the ventral surface round the blastopore, owing to the 

 greater development of the germ layers in that position. 

 In both shape and size the embryo under consideration sub- 

 stantially resembles the ovum. 



The next stage of development to be described is repre- 

 sented in the second figure on PI. 5. Besides being very 

 different in shape, the embryo in question is actually shorter 

 than the ovum. On the anterior end there are two pairs of 

 thickenings situated one behind the other. The blastopore 

 has been divided into two parts, one of which is situated im- 

 mediately behind the first pair of thickenings mentioned above, 

 but owing to the yolk which protrudes out of it and covers a 

 considerable portion of the ventral surface, it cannot be seen 

 in an external view ; the other is placed further back, and may 

 be similarly filled with protruding yolk. The quantity of 

 external yolk present seems to be highly variable, and in some 

 cases it appears to be wanting. When there is a great mass 

 of external yolk spreading over the ventral surface, nothing 

 can be seen save a botryoidal appearance, produced by the 

 yolk embedded in a sparse reticulum of ectodermal cytoplasm. 

 The presence of external yolk and its variability are points 

 in which the development of Eoperipatus resembles that 

 of Peripatoides (6). 



The posterior portion of the blastopore presents the appear- 

 ance of a square, the anterior side of which is absent. From 



