408 M. E. Hesse on the Pranizse and Ancei. 



The antenna are situated on the forehead, on each side of the 

 rostrum. The inner antennee generally reach only to the third 

 joint of the outer ones. They consist of four joints and a 

 terminal filament of three joints. The outer antenna present 

 four joints, with a terminal filament of seven joints. The eyes 

 appear like diflfused spots on the sides of the head. The thorax 

 is cylindrical, and composed of five segments, exclusive of that 

 forming the neck. 



The digestive apparatus, which is very voluminous, is easily 

 seen through the transparent skin ; but the author could not 

 trace the intestine to its inferior orifice ; nor could he detect the 

 circulation, except at the base of the abdomen upon the median 

 line. He distinctly perceived the movements of the blood- 

 globules in the branchial false feet : these globules arc subject 

 to a regular impulse from right to left. But in a female which, 

 after the expulsion of her young, was as it were reduced almost 

 to a mere skin, he was able to see that the globules of the blood 

 are subjected to two opposite movements — namely, a median 

 one towards the posterior extremity, and a lateral one directed 

 forwards. 



The globules are of equal size, of an oval form, and rather 

 wide apart ; they are subjected to a regular jerking motion, 

 comparable to the movement of the second-hand of a watch ; 

 they are driven to the furthest extremities of the appendages, 

 and here their motion appears to be more lively than at their 

 centre. The impulsion of the heart is manifested throughout 

 the median line, but is most sensible at the base of the thorax 

 at its junction with the abdomen. 



The nervous or ganglionic system is readily visible in young 

 individuals, in consequence of their transparency. The thorax 

 presents six ganglia, of which the first is cephalic, and the last 

 forms the base of the penis. The ganglia are lozenge-shaped, 

 and united by a double interganglionic cord, of which, how- 

 ever, the tubes are combined so as to leave no interval. Each 

 ganglion emits on each side a very delicate nerve, which traverses 

 the feet ; and the nerves of the fifth pair of feet emit a branch, 

 which descends from the base of the feet to the first abdominal 

 segment. 



The six ambulatory feet are composed of five joints, of which 

 the first and last are the longest ; the latter is terminated 

 by a strong claw. In the youngest larvae the first pair, attached 

 to the sides of the neck, do not present this construction. 



The abdomen likewise presents six joints, of which the first 

 five are of equal size, and the sixth, which is usually larger, is 

 of a triangular form. Each joint has a double pair of branchiae 

 or natatory feet : these are usually lamellar and ciliated, and at- 



