I0 BENSLEY. [VOL. II. 



of the adult is entirely formed by rapid growth from the short 

 non-glandular region of the early larva. 



One cannot doubt that the large saccular glands of the larval 

 Amblystoma are the homologues of the so-called oesophageal 

 glands of Proteus and Necturus. The failure of Kingsbury, 

 however, to detect the presence of zymogen granules in the 

 glands of Necturus led me to reinvestigate these structures 

 with a view of determining whether or not this was a real 

 point of difference. At first I employed a number of speci- 

 mens of Necturus which had been kept in the laboratory tank 

 for several months without food. In these cases the results 

 were negative, no zymogen granules were present. I after- 

 wards obtained two specimens captured in the vicinity of 

 Toronto, and in a perfect state of nutrition. In these no 

 difficulty was experienced in demonstrating the presence of 

 zymogen granules in the cells of the oesophageal glands. 

 Kingsbury's failure is, in all 'probability, to be ascribed to the 

 inadequate method he employed to demonstrate the granules. 

 For this purpose he employed treatment of the fresh glands 

 with osmic acid. Now it has been noted by Langley (7) and 

 Griitzner (3) that the protoplasm of ferment-secreting cells 

 which contain a great deal of reserve material (prozymogen) 

 stains strongly in osmic acid. For this reason 

 its use, in cases where the granules are few in 

 number and small, and where there is a great 

 deal of prozymogen present, is of little value. 

 This is precisely the condition in Necturus. 

 By the neutral gentian method, however, the 

 granules are stained much more strongly than 

 the prozymogen, and no difficulty is experi- 

 enced in demonstrating them when present, 

 s. Zymogenic Fig. 8 shows a number of cells from such a 



cells from oesophageal 



gland of Necturus, preparation. 



It should be added, however, that the oeso- 



ules in free border of 



cells, zeiss apoch. 2 phageal glands of Necturus do not present the 



mm., ocular 8. -, f r , . . 



evidences of strong functional activity seen in 

 those of the larval Amblystoma. The granules are much smaller 

 and may be quite absent from many of the cells of the gland, 



