652 'Journal of Comparative ISleurology and Psychology. 



in the brain) * * * ^s ^ J.^^g^ though not always, these 

 cells are much larger than III. 



"The cytoplasm is, especially distally, coarsely vacuolar, more 

 so than in any other ganglion cell; this gives the cell much the same 

 appearance as a slime-producing gland cell." 



CoE (1895) does not find cells of the fourth type in Cerebratulus 

 lacteus. 



The writer (Thompson 1901) has found in the brain of Zygeu- 

 polia litoralis one pair of neurocord cells, and a pair also in the 

 brain of Micrura caeca. 



b. The neurocord cells of Cerebratulus lacteus. — The present 

 investigation differs in one particular from those of the workers 

 quoted above, namely: in the number of the neurocord cells of 

 the brain. Here for the first time are described six pairs of cells 

 and one unpaired cell that in position, in size, and in structure are 

 undoubtedly neurocord cells. 



Structure. — For all thirteen cells the general form of the cell 

 body is broad and pear shaped, and the cytoplasm in most cells 

 stains but slightly and contains large vacuoles, although in a few 

 instances the cytoplasm is dark and densely granular. The 

 nucleus is either spherical or slightly flattened, and is always 

 found at the broad end of the cell. Both chromatin and nucleolus 

 are situated at the margin of the nucleus, the latter closely pressed 

 against the nuclear membrane. 



The following table gives the size and position of each neurocord 

 cell. 



TABLE OF NEUROCORD CELLS. 



Size and position. First pair. — The first pair of neurocord cells 

 is found in the region in which the oesophageal nerves originate 



