1 66 Mary I sab ell e Steele 



also tried upon two series of Palaemonetes, each series was com- 

 posed of a considerable number of individuals. Results, however, 

 were not particularly different from those obtained after removing 

 a part of the eye. 



A total of 600 Palaemonetes and hermit crabs had either one or 

 both eyes operated upon. A much smaller number of Crangon 

 and crayfish were used. No accurate account of the Ascellus, 

 Oniscus and Gammarus was kept. More than 50 per cent of the 

 Palaemonetes and hermit crabs died immediately, or within a 

 short time, after the operation, many of them dying within a few 

 minutes after the eye was injured. Of the survivors about 58 per 

 cent lived through one or more moults. 



Forty-two Crangon had the eye operated upon and of these one 

 died of the operation. The crayfish used were for the most part 

 C. gracilis, measuring from 12 to 15 mm. in length, that had 

 moulted but once after hatching. 



Palaemonetes and Crangon moult once about every ten days to 

 three weeks. The hermit crabs moult much less frequently, often 

 but once in two or three months. The hermit crabs regenerate, 

 however, as rapidly as Palaemonetes or Crangon. 



Considerable difficulty was experienced in keeping the animals 

 alive and in keeping individual records. Finally the plan of 

 keeping each animal in a separate finger bowl was adopted. This 

 method was fairly satisfactory except in very warm weather. 

 Then the water became warm and unless it was changed often the 

 animals soon died. Chopped-up bits of clam were fed to them 

 two or three times a week. Great care had to be used in warm 

 weather for the water became foul, if the food was left in more 

 than three or four hours, and caused the death of the animals. 



In spite of all precautions various accidents occurred which 

 resulted in the death of promising material. Twice attempts 

 were made to transfer the experiments from Philadelphia to 

 Woods Hole or vice versa with disastrous results in each case. 

 The failure was due in part no doubt to the extreme warm weather. 

 For although every known precaution was taken most of the 

 animals died within twenty-four hours. 

 .-^ A number of the ordinary fixing fluids were used to preserve 



