274 C. M. CHILD. 



Various other facts noted in the course of my experiments 

 require mention here. It was noted that regenerating tentacles 

 attained a greater length during the summer months than during 

 winter (cf. Child, '03/7). This difference is probably due, at 

 least in part, to the fact that the internal pressure is higher in 

 summer than in winter in consequence of the greater activity of 

 the cilia in forcing water in through the oesophagus (cf. Child, 

 'O4// 1 ). Local pressure must also vary in a similar manner. 



It was also observed in a large number of cases that the ten- 

 tacles of normal animals or regenerated specimens of C. solitarius 

 often began to shrivel at the tips in the manner described above 

 when the specimens had been kept in captivity and without 

 special feeding for two months or more. Frequently the margi- 

 nal tentacles were reduced to a length of 56 mm., the specimens 

 appearing otherwise healthy and in good condition, except that 

 the body was in all cases less distended than in newly taken 

 specimens. In the light of the preceding experiments the con- 

 clusion is justifiable that the tentacle-reduction in these species 

 is due to decrease in internal water-pressure. The gradual ex- 

 haustion of the pieces and the consequent diminution of ciliary 

 activity is without doubt one factor in the result. 



As winter approached it was noted that the atrophy of the 

 tentacles began sooner and proceeded farther. During De- 

 cember many of the specimens brought into the laboratory from 

 the bay possessed marginal tentacles only 8 10 mm. in length 

 with atrophied tips and -labial tentacles similarly reduced. In 

 nearly all specimens with the tentacles normal in appearance at 

 the time of taking, the atrophy of the tips began within a week 

 or two. 



In January and the early part of February, beyond which time 

 my observations do not extend, more than a hundred specimens 

 were taken and of these about 75 per cent, possessed reduced 

 tentacles with atrophied tips when taken. Many of the remainder 

 were specimens with regenerating tentacles, which had undoubt- 

 edly been injured. 



During the summer and autumn reduced tentacles with atro- 

 phied tips were not found on any specimen at the time of taking. 

 Moreover, the tentacles of summer and autumn specimens were 



