82 K. KTSHTNOUYE. 



appendage. It is well developed. From the segment of the fiftli 

 appendage backwards, a pah' of cœlomic cavities develop in every 

 segment. These cœlomic cavities develop at first in a dorsal and 

 posterior direction. The second and third cœlomic cavities are di\id- 

 ed into two ]iortions each — veutral and dorsal — as the cells forming 

 the middle ]^art of their wall become loose and fill up the cavity (figs. 

 14, 58). Tlie ventral portion of the second cœlomic cavity remains 

 as the coxal gland, while that of the third cœlomic cavity disappears 

 soon after its separation (fig. 14). From the fourth l)ackwards 

 cœlomic cavities gradually disappear from the ventrtd median portion 

 (fig. 55). The dorsal portion of the cœlomic cavity remains long 

 at the sides of the circulatory system (figs. 54-56); but it disappears 

 l)ef(^re the embryo hatches. The dors:d y)ortion of the second cœlomic 

 cavity elongates anteriorly and meets with tlie posterior end of the 

 first cœlomic cavity (fig. 17). 



Coxal Gland. 



The bi'ick-rcd gland of Packard is mesoblastic in origin, and tlie 

 liuuen of the gland is the remnant (^f a portion of the scond cœlomic 

 cavity. Tlie gland develops from the ventral p(^rti<in of the second 

 cœlomic caA'ity, which belongs to the segment of the fifth appendage. 

 Almost simultaneously with the separation of the cœlomic cavity into 

 the dorsal and ventral portions, (^ne laver of cells enclosing the ventral 

 portion is separated from the other mesoblastic cells, (which are used to 

 form connective tissue, muscles, entosternite, &c.,) and causes that 

 portion to have the shape of a sac or tube. The sac is the rudiment 

 of the coxal o-land. The cells forming- the wall of the o-land are 



