Organization of the Cyprides. 109 



ot our knowledge of the organization of tlie Crustacea, and it 

 was easy to foresee that with the extraordinarily perfected 

 methods of recent times, and especially the preparation of 

 serial sections from hardened and stained oljjects, numerous 

 gaps in our knowledge of these organisms would be filled up 

 without much dithculty. Consequently I only supjjlied a 

 pressing desideratum when I again took up the investigation 

 of Cypris. The results obtained are briefly summarized 

 here. 



1. The nervous system consists, besides the brain clothed 

 Avith a thick ganglionic covering, of an elongated ventral 

 cord containing five pairs of ganglia. Tlie anterior section of 

 the brain, representing the prosencephalon of the Arthropod 

 brain, gives forth the nerves to the tripartite frontal eye and 

 possesses a ])articularly strong coating of ganglion-cells, in 

 which the centre of projection of the highest rank is probably 

 to be sought. The mesencephalon gives off the nerves to the 

 anterior antenna?, into which, however, fibres from the prosen- 

 cephalon also enter ; at the sides of the metencephalon repre^ 

 seiited by the exceedingly elongated commissures, which only 

 unite far above the oesophagus, the nerves of the second pair 

 of antennjB originate. The ventral chain of ganglia extends 

 throughout the length of the body to the sexual apparatus, 

 and in its anterior, broader portion passes beneatli the pro- 

 jecting cariniform pectoral plate on the side of which the 

 maxillai and maxillipeds (second pair of maxillai) originate. 

 This section contains the closely approximated ganglia of the 

 mandibles, maxillae, and maxillipeds, the muscles of which 

 are supplied by the nerves issuing from them. Beyond the 

 jK'Ctoral plate commences the narrower and more elongate4 

 division of the ventral cord, the two ganglia of which give off 

 the nerves to the pairs of legs. At the posterior of these 

 terminates the cell-layer, which quite continuously coats the 

 concentrated ventral cord, and the longitudinal fibres of the 

 central mass are continued in two long median sten)s nearly 

 toucliing each other, which ramify among the muscles of the 

 abdomen. 



2. The frontal eye^ as in all groups of Crustacea, is tri- 

 partite and receives for each of its three divisions a nerve 

 which is rooted in the median layer of the prosencephalon. 

 Each of the three closely connected pigment-cups is occupied 

 by some sixteen to twenty cells, into which the fibres of the 

 nerve enter from the outside beneath a nearly spherical 

 lens. Thus the eye, like the lensless median eye of the 

 Cypridinaj and Phyllopoda {Branchipus) , is an inverse 

 cup-eye. I have found no cuticular divisions such as occur 



