H. M. FucHS 281 



the same animal as the eggs, (2) the same as the sperm, and (3) a third 

 animal. Similarly in Series E, where the blood caused a decrease in the 

 fertilization percentages, all three types are present. 



What must be the true explanation of the phenomenon is seen from 

 the following list giving the times after they were brought into the 

 Aquarium at which the animals were used for experimentation. 



Series A. Animals brouglit in from the sea the same day as the experiments 

 were made. 



Series B. Animals liad been in the laboratory two weeks. 



Series C. The same lot of animals as Series A, but used the following day. 



Series D. Animals brought in from the sea on the same day as they were used. 



Series E. The remainder of the same lot of animals used for Series D, but experi- 

 mented with two days afterward.s. 



For Series A and D, in both of which the blood caused an increase 

 in the percentages of eggs fertilized, the animals were brought in fresh 

 from the sea on the same day. For Series B, C, and E, on the contrary, 

 the animals used had been in the Aquarium circulation for lengths of 

 time varying fi-om one day to two weeks, and it was in these experiments 

 that the blood produced a decrease in the percentages. 



Evidently, then, even one night in the Aquarium water caused some 

 change in the composition of the blood of Ciona, causing it to reverse its 

 effect on the fertilizing power of the spermatozoa. It can hardly be 

 that this change is the first stage in the death of the animal, since all 

 unhealthy looking individuals were discarded, and animals such as were 

 used for the experiments were capable of living in the Aquarium circu- 

 lation in apparently good condition, for weeks after they were brought 

 in. That physiological changes occur in these animals, however, is seen 

 not only in the different behaviour of the blood described above, but in 

 the progressive decrease in egg-production, and in the fact that the eggs 

 are less and less pigmented each day'. 



For the experiments on egg-extracts and egg-waters of Ciona, which 

 have been described in the jjreceding sections, animals were used which 

 had been in the circulation for varjring lengths of time after they were 

 brought in from the sea, although most were used fresh the same day. 

 Results were, however, uniform, and the following experiment, made 

 with animals which had been five days in the Aquarium is further proof 

 that there is no change in the eggs as there is in the blood. 



' The eggs of Ciona which has been reared in the Aquarium are always more or less 

 unpigmented. 



