THE EMBRYOLOGY OF THE HONEY BEE 193 



pharynx, while a few fibres run from the anterior margin of the 

 central body of the tentorium to the posterior wall of the pharynx ; 

 both of these sets function as dilators of the pharynx. 



The muscles associated with the circulatory system will be 

 described under that heading. 



The fat body of the recently hatched larva has a decidedly dif- 

 ferent aspect from that in the old larva. In the latter the fat body 

 forms a compact mass filling the spaces of the body cavity and 

 composed of cells loaded with large fat globules, in figure 69A 

 represented by the empty spaces in the cells surrounding the 

 oenocyte. In the young larva, on the other hand, the fat body 

 never constitutes a compact mass, but is made up of a loose net- 

 work of branching cells (Fig. 69B) in only some of which a 

 minute fat globule can be made out. In the thorax the fat body is 

 somewhat more compact than in the abdomen, in which the fat 

 cells are much scattered, as shown in figure 75, iF, 2F, 3F. As in 

 Chalicodoma (Carriere and Burger 1897) the fat body is more 

 or less incompletely divided into three sections : a dorsal section, 

 situated above the dorsal diaphragm, the pericardial fat body 

 (Fig. 75, 3F), and two sections situated laterad on the mid- 

 intestine (iF, 2F) and divided from one another by the longi- 

 tudinal tracheal trunk. 



The circulatory system consists of the heart, the dorsal and 

 ventral diaphragms, and the blood corpuscles. 



The heart (Figs. XV, 75, 76, Ht) is a slender tube lying in the 

 mid-line between the mid-intestine and the dorsal hypodermis. It 

 extends from the twelfth trunk segment forward to the head 

 where it is continued as the aorta between the cerebral lobes, 

 lying immediately above the oesophagus. The anterior end of 

 the aorta opens into the body cavity. The posterior end is 

 closed. The lateral walls of the heart are relatively thick, 

 and contain the nuclei while the ventral and dorsal walls are thin, 

 the latter being in some sections so tenuous as to be scarcely 

 perceptible, the heart having the appearance of being closed dorsad 

 by the hypodermis (Fig. 75). Along the ventral side of the 

 heart is a narrow strip of cells, to which, in trunk segments seven, 

 eight and nine, the ovaries are attached. On its dorsal side the 

 heart is slightly indented by the intersegmental constrictions, while 



