178 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Many soft-shelled animals were obtained by keeping young crabs in 

 aquaria, and feeding them freely until ecdysis took place. 



Lobster larvte were hatched at the U. S. Fish Commission Station, 

 Wood's Hole, during June and July. They were reared, but with 

 great difficulty, up to the eighth moult. Fed on minced crab's liver 

 they throve well ; but unfortunately they also fed indiscriminately on 

 each other. 



Crangon was found in large numbers in the muddy bottom of the 

 Charles River ; crayfish were bought in the New York City markets. 



2. Methods. 



In sectioning, great difficulty was experienced, both on account of 

 the thickness of the chitin, which was often calcified, and because of 

 the siliceous otoliths, so numerous in the sacs of Macrura, and glued by 

 secretions to the hair tips. As the otoliths are insoluble in acids strong 

 enough to completely destroy organic tissues, the only successful 

 remedy was to remove them mechanically. This was best accomplished 

 by washing them out by a stream of water blown into the sac. The 

 apparatus for this consisted of a short piece of small rubber tubing into 

 one end of which was inserted a glass tube drawn out to a fine point. 

 The other end of the tubing being held in the mouth, and the capillary 

 tube inserted into the aperture of the otocyst, a stream of water was 

 driven into the cavity of the sac with considerable force. The larger 

 otoliths having been washed out in this way, fairly good sections could 

 be cut. 



In the crab, the difficulty in cutting the very thick calcified chitin 

 was obviated by using soft-shelled animals. The chitin is at this stage 

 very thin, uncalcified, and therefore more readily sectioned. Lobster 

 and crayfish antennules were decalcified by placing them in Gilson's 

 fluid for twenty-four hours, or in Vom Rath's platinic-osmic fixative 

 for a week or ten days. 



Of the many fixing reagents used, (1) Vom Rath's platinic-osmo-picro- 

 acetic mixture, (2) his corrosive-picro-acetic fluid, and (3) corrosive 

 sublimate plus 1 % acetic acid gave the best results and in the order named. 

 The last two were followed by staining in iron haematoxylin, which 

 gave a clear definite stain of sections as thick as 20//. The platinic- 

 chloride fixative of Vom Ruth was used for from three to five days, either 

 followed or not by treatment with pyroligncous acid. In Palasmonetes 

 and Crangon a fine diiferentiation of fibre tracts was obtained by using 



