THE STRUCTURE OF THE LARVA OF LANICE CONCHILEGA I 09 



are inclined to think is due to the fixation. The nucleus is surrounded by a 

 limited amount of cytoplasm, which by the use of appropriate stains can 

 be differentiated from the remaining contents of the cell. 



Stainiiig 7~eaction. Some of the sections were stained accordingto the 

 iron haennatoxylin method, others with Delafield's hsematoxylin followed 

 by an acid alcohol wash, and subsequently stained with blue carminé, 

 which we differentiated by washing in a weak solution of picric acid in ab- 

 solute alcohol. We hâve found this latter method give excellent results 

 with Poly'chœta generally, there being a considérable range in the differen- 

 tiation of glandular structures in particular. 



We hâve also obtained excellent results by staining sections in the 

 first place with alum carminé, and then with méthylène blue. Both, by this 

 method, and with hœmatoxylin and blue carminé the cytoplasm of thèse 

 cells is clearly differentiated from the other contents of the cell. 



If the gland is stained with hasmatox3'lin and blue carminé, the nu- 

 cleus appears of a reddish brown colour surrounded by the cytoplasm which 

 is stained with a délicate blue, whilst the remainder of the cells is of an 

 intense purple colour. In certain sections stained according to this method, 

 the tube which encloses the larva was included, and like the gland assumed 

 a deep purple blue. 



The resuit of using méthylène blue is still more striking, as the cells 

 \yith the exception of the nucleus and the surrounding cytoplasm are 

 stained with a brilliant blue, and at the same time patches of blue are 

 visible in the epithelium of the body wall and in the tentacles. If used after 

 alum carminé the nucleus is stained red and the cytoplasm a faint red, 

 the méthylène blue having no effect on thèse parts. 



The tube however is not stained with the méthylène blue. 



Entire larvse may be immersed for a short time in a weak solution of 

 méthylène blue, and then washed in water, this method shows up the dor- 

 sal gland very distinctly, and also reveals the présence of sécrétion in other 

 parts of the body. Safranin and thionin were also employed in some sec- 

 tions and were found to stain both the cells of the gland and the tube. 



The reactions of thèse différent stains point to the fact that thèse cells 

 secrète a mucous substance, and that the tube is composed of a similar 

 substance; and the conjecture is that this organ is the principal agent in 

 furnishing the material for the formation of the tube. 



It is possible that the mucin on leaving the gland undergoes some 



15 



