98 W. COLE ON A PARASITE OF HUMBLE BEES. 



muscular fibre. Indeed, the habits of the creature would render 

 such au element of structure quite superfluous. The adult leads a 

 perfectly inert and vegetative existence, immersed in the blood of 

 the bee, and deriving nourishment from the fluid by simple imbi- 

 bition. The body may be described as an elongated sac, having 

 only one aperture, that of the vulva ; there is no mouth or in- 

 testinal canal, and, as far as present observations extend, no trace 

 of nervous or circulatory systems. The interior of the body is 

 almost filled with two organs only, both comparatively of enormous 

 size — the fat-cells or corpus adipositm, and the ovary. The fat- 

 cells may be considered as the homologue of the intestine in other 

 nematoids. They form a sort of double chain, or row, which is 

 attached to the body at the extremities, but elsewhere lies free in 

 the general cavity. Each fat-cell is a membranous sac, sometimes 

 as much as about y T th of an inch in length, filled with a thick 

 fluid, containing granules, and " six to eight transparent nuclei, 

 which are of a tolerably even size, and about T ^Qths of an inch in 

 diameter." In younger specimens Sir John Lubbock found the 

 thick fluid contents of the cells replaced by an immense number 

 of minute vesicles ; in the interior of which were, in most cases, 

 a quantity of acicular crystals. In this stage the nuclei were 

 about ^^ths of an inch in diameter, and attached to the walls of 

 the fat-cell; they contained a number of small irregular bodies, 

 and were " surrounded by a sort of halo of granules." These cells 

 probably act as reservoirs of nutriment for the use of the animal, 

 and may also serve, in some measure, the office of an intestine by 

 still further elaborating the organized fluid in which the worm 

 lives. 



The ovary is a simple tube more than four times the length of 

 the body, in which it lies perfectly free, excepting in the neigh- 

 bourhood of the vulva, where it is connected with the fat-cells. It 

 commences as a fine tube at the anterior end of the body, gradually 

 increasing in size and coiling loosely amongst the fat-cells, until it 

 expands into a large uterus, which is generally quite extended 

 with ovae. It then contracts about one-half, and opens externally 

 at the end of the body opposite to that at which it commenced. 



The eggs afford excellent material for the study of yolk-segmenta- 

 tion and development, as from the transparency of the envelope the 

 various processes are readily observed. They may generally be 

 found in all stages ; from the clear, simple cell at the upper end of 



