LiTEiiAKY Notices. xxxv 



as, according to my observations, all the eyes belong to the third 

 segment. 



The concentration of the nervous system toward the cephalothorax 

 continues until the lateral ganglionic chains are united into one and 

 form the sub-cesophageal ganglion. The inner portion of the ganglion 

 becomes finely fibrous. The abdominal ganglia gradually atrophy and 

 attach themselves to the posterior end of the sub-CESophageal ganglion. 



The plates are well executed, though lacking in detail. 



Nervous System of Serpula(i). 



"The nervovis system is quite highly developed, the cerebral 

 ganglion attaining a diameter of .5 mm. in specimens whose whole body 

 diameter was 1.4. This ganglion gives oft", in front, two large branchial 

 nerves, which supply the branchi;e and two smaller nerves to the 

 oesophagus. A single nerve from its posterior, ventral, median edge 

 runs to the posterior part of the oesophagus. 



The cerebral ganglion gives oft", on either side, a large commissure, 

 which passes down around the oesophagus and into the large ventral 

 ganglion of the corresponding side." The ventral chain continues 

 through the entire body with a ganglion for each segment. The sub- 

 o^sophageal ganglion has three transverse commissures, and the others 

 which decrease backward have but one. About two-thirds of the mass 

 of the cerebral ganglion is made up of cells, while the inner portion is 

 composed of fibres. The other ganglia contain but few cells, arranged 

 on the outer surface. 



"At its posterior end, the dorsal portion of the cerebral ganglion is 

 prolonged into a most remarkable process; from the dorsal, posterior 

 corner on either side a large lobe passes outward and backward, and 

 then, bending suddenly downward, passes into the first ventral ganglion. 

 It will be seen that we have here, in reality, two pairs of oesophageal 

 commissures." 



Development of the Brain of the Horse-shoe Crab. (2) 



"The nervous system arises from a paired, longitudinal thickening 

 of the ectoderm. The anterior ends of these thickenings are much 

 broader than the posterior parts, and there are two pairs of ectodermic 

 invaginations. These parts form the brain. About twenty-four days 

 after fertilization nine pairs of ganglia may be seen (there is a pair in the 

 metastoma). They are separated from the general ectoderm from the 

 anterior end gradually. From the third pair of ganglia, backwards, 

 there is a lateral commissure in each segment. The brain has one 

 transverse commissure. 



1 Treadwell, a. S., " Preliminary Note on the Anatomy and Histology of Serpula 

 Dianthus," Zool. Anz., XIV, 370, p. 276. 



2 KiSHiNOUVE, K., " Preliminary Note on the Development of I.imulus Longispinis," 

 Zool. Anzeiger, XIV, 369, pp. 264-266. 



