RESEARCHES IN HELMINTHOLOGY AND PARASITOLOGY. 35 



tremity of it, corresponding to the head, had become translucent from 

 a solution of the granular matter within. The other or tail end 

 was subacute. The twelfth day the translucency had extended 

 itself to the interior part of the embryo, the extremity of which had 

 advanced beyond the others and presented an emargination commu- 

 nicating with an orifice opening into a canal visible in the interior, 

 and from the edge of the extremity was developed a circle of short 

 filaments which projected downwards and outwards. From the 

 thirteenth to the fifteenth days the granular matter had entirely 

 undergone a solution within the anterior half of the embryo, and 

 the latter had become somewhat dilated. The interior canal was 

 also more distinct, and the bordering filaments of the extremity 

 were larger. In the course of the sixteenth to the eighteenth day 

 the translucent half of the animal was separated from the other by 

 a constriction, and the canal in the interior presented at its anterior 

 portion a clavate tubular body, the free end of which projected 

 from the oral aperture. The extremity of the head was surrounded 

 by a reflected collar, from the free border of which projected the 

 filamentary appendages. The posterior half of the embryo was 

 still granular in appearance, but had become rounded and somewhat 

 dilated at the extremit}' . From the nineteenth to the twentieth day 

 the embryo alternately retracted and protruded the tentacular or fila- 

 mentary appendages, and the integument of the anterior half of the 

 body appeared to be getting annulated, which was distinctly so by 

 the twenty-first dsLy. The granular matter in the posterior part of 

 the body was also undergoing solution from the periphery towards 

 the center, and at its posterior part there appeared several large oil 

 globules. On the twenty-second day the annulations of the ante- 

 rior half of the body were very distinct, -the posterior half was also 

 becoming annulated, and near its extremity I for the first time ob- 

 served an anal orifice and one to four small epidermal spines. On 

 the twenty-fourth day the tubular clavate organ before mentioned, 

 occupying the anterior part of the alimentary canal, was alternatel}' 

 protruded and retracted as a proboscis. The proboscis, when fully 

 protruded, brought into view at its base a second circle of tentacu- 

 lar filaments within the first. On the twenty-sixth day the embryo, 

 when pressed from the egg, progressed forward by moving the pos- 

 terior half of its body from side to side, and it alternately pro- 

 truded and retracted the proboscis and the two circles of tentacular 

 filaments. When all the latter organs were retracted the head pre- 

 sented a truncate or depressed surface, and in their protrusion the 

 extremities of the outer circle of tentaculae and the end of the pro- 



