OSTRACODA. 387 



vided with two long lateral hepatic tubes (L), which may project 

 between the lamellae of the shell. The anus opens near the 

 base of the abdomen either dorsal or ventral to the caudal fork. 

 A saccular heart is present in most Myodocopa on the dorsal 

 surface, where the shell is connected with the body. It is absent 

 in most if not all Podocopa. The function of respiration is 

 performed by the inner lamella of the shell, as well as by 

 the whole surface of the body, over which an uninterrupted 

 current of water is maintained by the swinging movements of 

 the fan- shaped setose plates. There are no true branchiae 

 en the appendages, but in some Cypridinidae there is a double 

 row of leaf-like branchial structures on the back, near the last 

 pair of limbs. 



Two sets of glandular structures which appear to correspond with the 

 excretory organs of other Entomostraca are described by Claus. An 

 extensive gland, sending a process between the lamellae of the shell, has 

 been traced into the base of the posterior antennae, though the opening 

 was not detected. Smaller glands opening on the basal joint of the 

 second maxillae correspond with the shell glands of other forms, though 

 in the Ostracods they do not extend into the shell. The so-called Spinn- 

 drusen of the Cytheridae which open on the elongated exopodite (vide 

 infra, Cytheridae) of the second antenna belong, apparently, to the 

 category of cutaneous glands. 



Generative organs. The sexes are always separate and are 

 distinguished by well-marked differences in structure. The 

 males possess appliances on different appendages in Cypridina 

 on the second antennae, in Cypris on the maxilliped for holding 

 the females ; or a pair of legs (the first thoracic) may be 

 modified for this purpose (Halocypridae). In addition a large 

 copulatory organ, often possessing a complicated structure, 

 is always present. It is, however, not homologous in the- 

 several families, as will appear below. In the Cypridinidae 

 the testes are simple rounded bodies and the vasa deferentia 

 run directly to a median opening common to them both just 

 in front of the anus. A pair of appendages situated on either 

 side of the opening and probably representing the brush- 

 shaped organs of some of the Podocopa is, in this family, 

 modified as copulatory organs. In the Cypridae there are 

 four elongated or rounded lobes of the testis on either side, and 

 the vasa deferentia are connected by a canal passing from 

 one to the other, which may be of great length and thrown 



