92 University of California Publications in Zoology 



The histologieal elements found in the connective tissue net- 

 work of the gland, in addition to pigment cells, are of three 

 kinds: (1) large, clear cells with small, deeply staining nuclei 

 (pi. 11, fig. 2, eryth.) ; (2) large cells more or less deeply clouded 

 with blue in material stained in haemotoxylin, and showing evi- 

 dence of reticular chromatin network (pi. 11, fig. 2, leuc.) and 

 (3) cells filled with masses of granules staining deep red with 

 eosin, and yellow with picro-fuchsin (pi. 11, fig. 2, gran. m.}. 



The first cells above mentioned seem to be erythrocytes, as 

 they have precisely the same appearance as those filling the 

 vessels in the pia mater, where they are associated with fairly 

 numerous leucocytes. They are scattered freely throughout the 

 gland, entirely independent of vessels of any sort. This is very 

 remarkable for an animal which has a closed blood system, and 

 no explanation for such a phenomenon, if they really be erythro- 

 cytes, has yet been found. These cells range from eight to ten 

 microns in diameter, are clear and transparent, with small, 

 round, deeply-staining nuclei, and are irregular in outline. 

 though this may be due to slight shrinkage or contact with other 

 cells. 



The second cells above described have much the appearance 

 of large leucocytes. They are very uniformly round in outline, 

 and vary from seven to nine microns in diameter. 



The most peculiar and characteristic element present, how- 

 ever, are the numerous cells filled with granules. The granules 

 are about one and a half microns in diameter, and are very 

 nearly the same in size as the melanin granules in the pigment 

 cells. Where a pigment cell and a mass of granules have been 

 cut in close proximity and both types of granules slightly scat- 

 tered, it is difficult to distinguish them except by color. As 

 stated above, they stain a very deep red with eosin, suggesting 

 eosinophile granules in leucocytes, but they are larger and occupy 

 the cell more completely, as figured by Rawitz (1900). With 

 picro-fuchsin, on the other hand, they stain a deep yellow, similar 

 to the color given to muscle fibres. In many of the vessels of the 

 gland, especially in the larger ones, there are areas filled with a 

 substance which strongly suggests granules in process of disin- 

 tegration, and occasional scattered granules still intact may be 



