MUSEUM OF COMrAllATlVE ZOOLOGY. 



117 



which it had cost him niucli time and labor to obtain, but also for his 

 direction and many valuable suggestions. 



Tabulated List of Fishes studied. 



Killing 

 lleagent. 



Mcrkol's 

 fluid. 



Ugn., 



(hot). 



Jlerkd's 

 fluid. 



90 per cent 

 alcohol. 



Picro-sul- 

 phuric 

 acid. 



2 per cent 



chromic + 



acetic (few 



drops). 



Alcohol. 



Died, 90 per 

 cent ale. 



Condition. 



Local aggregations of spongy connective 

 tissue. 



Bony scale beginning to be formed. 



Spines being formed. 



Few spines. 



Edges of scale beginning to overlap. 



Mature spines all over scales. 



Spines all over scale ; no ganoin layer. 

 Epidermis degenerated ; thin ganoin layer. 



Spines on edges ; thin ganoin Layer. 



Few spines on edges ; thicker ganoin layer 



Kcceived from 



Dr. Mark. 



Prof. Birge. 

 Dr Mark. 



Mr S. P Bartlett. 

 Prof Reighard. 



The method used has been chiefly the preparation and study of 

 series of sections. In all except very young stages it was necessary to 

 decalcify the material before it conld be sectioned, and even after 

 decalcification sections in most cases could not be cut thinner than 

 15 fi, and often in the later stages it was necessary to make them 

 between 20 and 30 fi thick. For decalcifying I used 90% alcohol to 

 which was added a small quantity of 10% hydrochloric acid (in the 

 ratio of about 3 to 1). The tissue was usually left in this acid alcohol 

 twenty-four hours or more, and then soaked in several changes of fresh 

 alcohol to remove all traces of the acid before staining. Sections pre- 

 pared by grinding down scales have also been studied, as well as scales 

 freed from the soft tissues by treatment with caustic potash. Only by 

 the use of the latter reagent was I able to get a satisfactory knowledge 

 of the spines which cover the scale in its immature state. 



The stains which have given the best results are Boehmer's alum 

 haMiiatoxylin and Kleinenberg's hfematoxylin. As a nuclear stain the 



