3O2 CHARLES ALBERT SHULL. 



cess in destroying bacteria and fungi, and without injury to the 

 crayfishes, provided they are washed thoroughly several times in 

 plenty of pure water after the bath to cleanse their gills of the 

 copper sulphate. 



Young crayfishes are voracious creatures, and need to be fed 

 frequently. I have fed them every day with entire success, but 

 they soon tire of a uniform diet. Several kinds of food were used ; 

 and by rotation, so that they never received the same kind of food 

 on successive days, their appetites were retained. Fresh raw beef 

 was given them twice a week, and raw potatoes and pieces of Myr- 

 iophyllum, which was kept growing in the laboratory, were used 

 as vegetable foods. The Myriophyttum was covered with slime, 

 which was found to contain unicellular algne, rotifers, nematode 

 worms, annelids, such as sEolosoina kcmprickii, and other kinds of 

 small animals. This slimy material was especially esteemed, and 

 probably most nearly represents their normal diet. This food 

 material was left in the glass with the animals for an hour or two, 

 after which the remains were removed and fresh water placed in 

 the vessels. 



Using these methods, I have kept them alive for months in 

 perfect health, with rapid growth during the moulting season. 

 Occasionally a death would occur among them, but these fatalities 

 were always obviously due to special causes, not to any general 

 defects in the methods employed. 



After ecdysis the cast off exoskeletons were used in the prepa- 

 ration of the drawings. 



EXPERIMENTS. 



The experiments here described are a few typical ones selected 

 from a series, all of which gave similar results. The numbers 

 correspond to those used while recording notes on individual 

 experiments. 



No. 4. C. (Bartonius) bartoni, ?. Fifth right abdominal ap- 

 pendage removed March 24, 1907. The appendage was cut off, 

 leaving a short stump attached to the body (Fig. 4). 



The first moult occurred in the afternoon of March 27, three 

 days after the operation. No regeneration could be noticed, but 

 the wound was perfectly healed (Fig. 5). The second moult 



