22 Journal of Comparative Neurology. 



which occurs in front of the paired eyes, because he thought 

 that the presence of that eye renders quite probable the 

 hypothesis that the compound eyes of the Cypridce 

 are analogous to those of the Cladoccra. According to 

 Dr. Claus this median simple eye consists of three layers; 1st, 

 an outer transparent lens ; 2nd, an inner nervous layer ; 3rd, an 

 intermediate pigment layer. Both in form and position the 

 outer portion of this eye resembles the lens of the Heteropod eye. 

 The non-pigmented striated portion, into the substance of which 

 nerve fibres penetrate, contains elongated cells. Later Dr. 

 Claus (5) showed that in Cypridina the size and position of the 

 paired eyes serve to differentiate the sexes. In the males, the 

 paired eyes are almost in the middle of the shell, while the much 

 larger, unpaired, median eye is imbedded in a swelling of the 

 forehead. In 1891, Dr. C. Claus (6) stated a theory concerning 

 the compound eyes of the Ostracoda. 



Dr. Rehberg (9) also has contributed something to further 

 this cause. Among other things he has minutely and accurate- 

 ly described the tip of the second foot of Cypris. In his eyes, 

 this member is something more than a leg functioning as an 

 ovipositor, for in its tip it bears a sensory organ which is proba- 

 bly auditory in function. In addition to this he has described, 

 in the following manner, the sensory seta found on the third 

 joint of the antenna. This sensory seta consists of: 1st, a 

 chitin-surrounded proximal portion ; 2nd, a short transparent 

 middle-piece ; 3rd, a granular knob-like distal portion. Its nerve 

 enters through a hole in the chitinous exoskeleton. 



Later Dr. Lang (8) summarized the accessible literature 

 on the central nervous system of the Ostracoda in the following 

 words: " The ventral chain of Cythere, which follows the brain 

 and circum-oesophageal commissures, is said to consist of an in- 

 fra-oesophageal ganglion and four subsequent ventral ganglia. 

 The infra-oesophageal ganglion is said to show its composition out 

 of two ganglia and to innervate the jaws, while the three subse- 

 quent ganglia give off nerves to the limbs, and the last ganglion, 

 nerves to the most posterior divisions of the body and the genital 

 apparatus. In contrast with the above, the ventral chain oi Halo- 



