No. I.] PECTORAL APPENDAGES OF PRIONOTUS. 1 83 



shrinking away of the web between the rays, apparently by 

 absorption. This gradually increased until first the outer parts 

 of each ray were free (Fig. 2). The fish now measured 14 

 mm. in length. Toward evening of the second day, when the 

 fish was 17 mm. in length, the rays were almost entirely free, 

 only a very small portion of the connecting membrane remained, 

 (Fig. 3) and this eventually disappeared. The process was 

 almost identical in several other specimens which were ex- 

 amined. 



Methods. 



In studying the anatomy of the nerve-supply of the pectoral 

 appendages, the anterior half of the body was macerated from 

 one to three days, according to the size, in 40^ nitric acid. 

 This was rendered necessary by the thick osseous covering of 

 the head of the fish. In the dissection of these acid prepara- 

 tions, porcupine quills were used. 



The nerves when freed from the muscles and connective 

 tissue were preserved in 70^ alcohol. 



For the study of the histology of the free rays, the following 

 reagents gave satisfactory results : Kleinenberg's picro-sul- 

 phuric acid, osmic acid, Merkel's fluid, and Miiller's fluid. The 

 specimens were washed and preserved in alcohol, passing from 

 50/0-70%, where they remained until used. 



The results obtained by the use of Merkel's fluid were in 

 some respects the most satisfactory. The parafflne method 

 was used for obtaining sections which were cut 5 mm. in thick- 

 ness. The tissues were stained, in mass, with Delafield's 

 haematoxylin or borax carmine. In studying the peripheral 

 terminations of the nerves in these rays, Dogiel's (9) method 

 of using methylen blue gave very suggestive results, but the 

 picrate of ammonia, used to fix the blue, macerated the epider- 

 mis so that the ultimate nerve-endings could not be studied as 

 carefully as would have been possible if the epidermis could 

 have been sectioned in place. The best demonstration of the 

 nerve-endings which I obtained, aside from Golgi, was by the 

 use of Mitrophanow's gold chloride method as quoted by Ma- 

 callum (7). Perfectly fresh tissue was treated with a i % solu- 



