52 CHARTODERMA HAWAIIENSIS. 



in hand, two distinct kinds of material are secreted, but in widely differing 

 (luantities according to the locality. The cells attached to the gonad are usually 

 more or less pyriform with comparatively small, dense almost homogeneous 

 nuclei placed basally, while the remaining protoplasm is closely packed with 

 innumerable granules. By far the greater number of these are spherical and of 

 yellow or slightly greenish yellow tint. They are liberated, as is the secretion in 

 the more anterior parts of the gut, by the constriction of droplets from the distal 

 end, and may be seen undergoing disintegration and solution in many different 

 places. Among the granules of this character are others in the form of small 

 particles of a distinct pink or violet color after treatment with haematoxylin. 

 They have every appearance of being an end product and not a stage in the 

 . development of the more abundant secretion. 



Elsewhere in the gland the cells are of looser texture, the basal nuclei are 

 relatively larger and granular and many if not all contain the two species of 

 secretion just described. Generally the yellowish product is scant in amount, 

 while in many cells the violet tinted substance accumulates in spherical or 

 elliptical masses, surrounded by a vacuole in preserved specimens, that almost 

 fills the cell. These secretory products are passed out entire, and in a single 

 section as many as twenty-five may hold positions in the lumen of the gland. 

 Making their way forward many if not all pass into the intestine, and here may 

 be seen in various stages of solution, forming at first a vacuolated product that 

 before dissolving completely transforms into a finely granular material of maroon 

 color after treatment with haematoxylin. 



The cells of the intestine are cubical in form and in front of the pericardium 

 show signs of slight glandular activity. Behind this point this phase of activity 

 disappears, and cilia become developed and continue to the opening into the 

 cloacal cavity. 



The large size of the ganglia and the abundance of the nerve cells that 

 envelop them and also the sharpness of even the smaller nerves renders it pos- 

 sible without nmch effort to gain a very clear idea of the nervous system of this 

 species (see Plate 7, fig. 2). As is there shown the brain, located some dis- 

 tance above the digestive tract, is distinctly enveloped in a delicate connective- 

 tissue sheath and is clearly bilobed in form though its outlines are somewhat 

 obscured by great masses of ganglion cells (forming the precerebral ganglia) 

 attached chiefly to its lateral and anterior surface. A considerable number of 

 delicate fibres, passing out from the brain, attach to these ganglionic bodies which 

 in turn are connected with large numbers of nerve fibres that pass chiefl}^ to the 

 walls of the mouth and the frontal sense organ. 



