Thompson, Brains of Cerebratuhis. 651 



geal nerves, and numbers of neurocord cells are irregularly dis- 

 tributed along the lateral cords. In the Metanemerteans, Drepa- 

 nophorus and Prosadenophorus, Burger found that a single pair 

 of neurocord cells occurs in the brain, but that these cells are 

 entirely absent from the lateral cords. 



Burger (1895) p. 320 states "Bei C. marginatus sieht man auf 

 einem Querschnitt, welcher die ventralen Ganglien an der Abgang- 

 stelle der Schlundnerven getroffen hat, zwei Ganglienzellen von 

 ungewohnlicher Grosse einander gegeniiber liegen, welche um so 

 mehr auffallen, als in diesem Abschnitt des Gesammthirnes nur 

 die kleineren Formen herrschen ** * " He gives the measure- 

 ments of neurocord cells in two different genera. In Cerebratulus 

 marginatus the diameter across is 20//, the length 40/i, in Langia 

 formosa the diameter across is i2/<, the length 40//. 



Montgomery (1897) finds in Cerebratulus lacteus three pairs 

 of neurocord cells in the ventral brain lobes, and, like Burger, 

 a large number at unequal intervals along the lateral cords. 

 Montgomery states that the first pair of cells lies in the same sec- 

 tion with the beginning of the oesophageal nerves. The third pair 

 lies six sections behind the first, and the cells that compose the 

 second pair, which are not in the same frontal plane, lie between 

 the first and the third pairs. On pp. 402 to 403 the structure of 

 these cells is described. "The structure of the giant ganglion 

 cells IV of Cerebratulus (figs. 27 to 29, 32) has much resemblance 

 to that of cells III of the same species, though there are certain 

 differences which may usually serve to distinguish them. 



"The nucleus (fig. 31, a-e) may be nearly spherical but is more 

 frequently spherico-oval. It usually has a proximal position 

 within the cell, close to the cell membrane, is seldom central and 

 never distal in position. In it small masses or granules of chro- 

 matin {chr.) of adequal size are arranged peripherally on the 

 inner surface of the well-marked nuclear membrane; and these do 

 not form a continuous layer, as is frequently the case in the nucleus 

 of III, but are placed at more or less regular distances apart. * * * 

 A thin mass of chromatin envelops the nucleus {n). The latter 

 is never absent, is of large size, and almost always peripherally 

 situated; it has thus the same position in the nucleus as the latter 

 has in the cell * * * The cell (figs. 27 to 29, 31) is 

 unusually of a shortened pyriform shape, occasionally nearly 

 spherical, or again elongated (this is the case with the first pair 



