IX. The Brvozoa 



ECTOPROCTA. 



About the earliest observations on the nervous system of 

 these animals was by Dumortier and Van Beneden in 1843. They 

 described the central nervous system of fresh water forms as com- 

 posed of two ganglia above the oesophagus joined by commissures. 

 From the aboral part of the ganglion a pair of nerves runs to the 

 oesophagus. They also considered that a pair of nerves supplied 

 the epistome. 



In 1848 Van Beneden speaks of but a single ganglion. 



Allman, 1856, in fresh water forms describes a single unpaired 

 oval ganglion. The two oesophageal nerves are represented as an 

 oesophageal ring with enervation for the epistome. 



Hyatt, 1865-1868, describes the central ganglion in Phimatella 

 with the ganglion concentrated. The two long arms of the animal 

 however, are capable of independent movement. The ganglion in 

 Trederecella is spindle-shaped. In Plumatella the ganglion is kid- 

 ney-shaped and as it doubles upon itself by movements of the 

 animal it becomes heart-shaped. He describes a true nerve ring 

 about the oesophagus. Nerves go to the middle and end intestine. 

 Hyatt also describes nerves to the epistome and to the tentacles. 



Nitche, 1869-76, has studied bryozoans quite extensively. He 

 found a central cavity in the ganglion in embryonic stages. He 

 recognized an oesophageal ring, intestinal nerves, tentacle nerves. 

 He recognized on the tentacles bristles which he called taste bristles. 



Claparede, 1871, in some bryozoans describes the nervous sys- 

 tem of colonial forms ; nerve strands running the length of the body 

 were recognized. 



Kraepelin, 1887, found the center of the ganglion in adult 

 forms, and the shape of the ganglion of fresh water forms elipsoid. 

 He also recognized peripheral ganglion cells in the ganglion. Oral 

 nerves were seen, as well as nerves to the epistome. 



Verworn, 1887, in a general way recognized ganglion cells. 



Saefftiger, 1888, has especially added to our knowledge of the 

 distribution of the nerves to the tentacle crown ; he also considers a 

 sympathetic system but says nothing of the sense cells in the ten- 

 tacles although he describes the epithelium of parts of the animal. 



Braem, 1890, describes the central ganglion of fresh water 

 forms as hollow with an outer thinner oesophageal and a ventral 

 thicker wall. He considers the inner part of the ganglion as largely 

 fibrous. 



Oka, 1891, has considered fresh water forms, especially Pec- 

 tinatella. Like Saefftiger, he finds the ganglion with a cavity in 

 the mature state. The ganglion is compared to a spindle bent in 



