II REPRODUCTIVE ORGANS 31 



small ganglionic enlargements occur. In Apodidae, on the other 

 hand, those segments which carry more than one pair of 

 appendages have as many pairs of ganglia, united by transverse 

 commissures, as they have limbs. 



A stomatogastric nervous system exists in Apus, where a 

 nerve arises on each side from the first post-oral commissure, 

 and runs forward to join its fellow of the opposite side on the 

 anterior wall of the oesophagus. From the loop so formed a 

 larger median and a series of smaller lateral nerves pass to the 

 wall of the alimentary canal. A second nerve to the oesophagus 

 is given off from the mandibular ganglion of each side. 



Reproductive Organs. In Chirocephalus the ovaries (Fig. 

 2, Ov) are hollow epithelial tubes, lying one on each side of the 

 alimentary canal, and extending from the sixth abdominal 

 segment forwards to the level of the genital opening : at this point 

 the two ovaries are continuous with ducts, which bend sharply 

 downwards and open into the single uterus contained within 

 the projecting egg-pouch and opening to the exterior at the 

 apex of that organ. Short diverticula of the walls of the uterus 

 receive the ducts of groups of unicellular glands, the bodies of 

 which contain a peculiar opaque secretion, said to form the egg- 

 shells. In Apodidae the ovaries are similar in structure, but 

 they are much larger and branch in a complex manner, while 

 each ovary opens to the exterior independently of the other in 

 the eleventh post-cephalic segment ; nothing like the median 

 uterus of the Branchipodidae being formed. The epithelium of 

 the ovarian tubes proliferates, and groups of cells are formed ; 

 one becoming an ovum, the others being nutrient cells like those 

 which will be more fully described in the Cladocera, 



In Chirocephalus the testes are tubes similar in shape and 

 position to the ovaries, each communicating in front with a 

 short vas deferens, which dilates into a vesicula seminalis on its 

 way to the eversible penis ; an essentially similar arrangement 

 is found in all Branchipodidae, but in Apodidae and Lininadiidae 

 there is no penis. 



All the Branchiopoda are dioecious, 1 and many are partheno- 

 genetic. Among Branchipodidae Artemia is the only genus 

 known to be parthenogenetic, but parthenogenesis is common in 



1 Bernard's statement that Apus is hermaphrodite seems based on insufficient 

 evidence. 



