300 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



body wall on either side, but nearer to the ventral than the 

 dorsal aspect, is a close-set series of transversely placed shallow 

 depressions, which give the body wall a crenated appearance 

 along two lateral lines. The depth and distinctness of these 

 depressions vary considerably in different conditions of contrac- 

 tion of the body wall. 



Mouth and anus are absent. 



Under the cuticle is a thin hypodermis, with nuclei at regular 

 intervals. The muscular system is poorly developed, but exists 

 as a single layer of cells in close connection with the hypodermis. 

 These cells show a loose arrangement into longitudinal rows 

 along the ventral side, and less markedly into transverse rows 

 on the dorsal side of the body wall. There are two well-marked 

 lateral absorptive lines. 



The greater part of the space internal to the muscular layer 

 is occupied by a coarsely vacuolated or reticular tissue, which 

 has large nuclei, surrounded by protoplasm here and there in 

 its substance. This tissue is continuous from near the anterior 

 to near the posterior extremity, is moderately tough, and can 

 be shelled out from the other structures. It contains an 

 irregular central cavity, which ends blindly at either extremity. 

 The ovary is single, ventrally placed, and forms a strand of 

 opaque white tissue almost as long as the worm itself. The 

 ova all ripen at the same time, and, increasing in size, com- 

 press the other structures, particularly the muscular layer and 

 the reticular tissue. The early development of the ova takes 

 place inside the body of the female. The segmentation is 

 total and unequal, and is followed by a modified gastrulation. 

 Meantime the ova or young embryos separate from one another, 

 thus taking up more space, and still further compressing the 

 other structures, so that the body of the parent becomes ex- 

 tremely fragile — being, indeed, little more than an elongated 

 sac filled with eggs or embryos. I estimated that my largest 

 specimen contained upwards of 20,000,000 embryos. 

 Excretory canals are entirely absent. 



The nervous system seems to be represented by a thickening 

 of the hypodermis at the head end, which is not continued 

 backwards into definite longitudinal cords, except, perhaps, for 

 a short distance on the ventral aspect. 



