3O CRUSTACEA BRANCHIOPODA CHAP. 



has rather more, and the blood of Apus is very red. 

 The only other Crustacea in which the blood contains haemo- 

 globin are the Copepods of the genus Lernanthropus, 1 so that the 

 appearance of this substance is as irregular and inexplicable in 

 Crustacea as in Chaetopods and Molluscs. 



The nervous system of Branchipus may be described as an 

 illustration of the condition prevailing in the group. The brain 

 consists of two closely united ganglia, in each of which three 

 main regions may be distinguished; a ventral anterior lobe, a 

 dorsal anterior lobe, and a posterior lobe. The ventral anterior 

 lobes give off nerves to the median eye, to the dorsal organ, and 

 to a pair of curious sense -organs, comparable with the larval 

 sense-knobs of many higher forms, situated one on each side 

 of the median eye ; in late larvae Glaus describes the 

 terminal apparatus of each frontal sense-organ as a single 

 large hypodermic cell; W. K. Spencer 2 has lately described 

 several terminal cells, containing peculiar chitinous bodies, in 

 the adult. The homologous sense-organs of Limnetis are appar- 

 ently olfactory. The dorsal anterior lobes give off the large 

 nerves to the lateral eyes, while the posterior lobes supply the 

 first antennae. The oesophageal connectives have a coating of 

 ganglion -cells, and some of these form the ganglion of the 

 second antenna, the nerve to this appendage leaving the con- 

 nective just behind the brain. The post-oral nerve-cords are 

 widely separate, each of them dilating into a ganglion opposite 

 every appendage, the two ganglia being connected by two 

 transverse commissures. The ganglia of the three cephalic 

 jaws, so often fused in the higher Crustacea, are here perfectly 

 distinct. ( 'losely connected with each thoracic ganglion is a re- 

 markable unicellular gland, opening to the exterior near the 

 middle ventral line; it is conceivable that these cells may be 

 properly compared with the larval nephridia of a Chaetopod, 3 

 but no evidence in support of such a comparison has yet been 

 adduced. 



Px'hind the genital segments, where there are no limbs, the 

 nerve-cords run backwards without dilating into segmental 

 ganglia, except in the anterior two abdominal segments where 



1 [The re.il pigment in L<'i-rtnt/(i-i>/>iiK. see p. 68, luis been shown to be not 

 liJM'iiio.nlubiii, so tliat the presence of this substance in Phyllopod blood becomes 

 doubtful (r.S.] -' /fitst-lir. wiss. Zool. Ixxi., 1902, p. 508. 



:! Cf. Gaskell, Jotirn. Anut. I'hysiol. x., 1876, p. 153. 



