176 W. A. KEPNER AND P. N. JESTER. 



glasses and given no food. Another lot of six were isolated. 

 These were used as controls and were kept supplied with food 

 in the form of Cyclops and daphnids. The observations were 

 kept up until April 13, during which time, one of the controls had 

 died (March 22) but none ot these controls had lost part of their 

 tentacles. Except for the one specimen dying, the controls at the 

 end of the period of observation were in excellent condition and 

 showed no negative features. The starving specimens presented 

 a marked contrast to the control series for by March 22 two 

 specimens had died. Of these two that had died, one had lost 

 more than two thirds the length of each of its tentacles the day 

 before it had died. The four other specimens, by April 14, had 

 lost parts of their tentacles. The most conspicuous individual 

 in the starved series was designated specimen six in our records. 

 Figure 5, A, represents the contour of this animal when expanded 

 at the time of isolation. On March 24 it showed, in the expanded 

 condition, that its tentacles were shorter and knobbed on the end 

 (Fig. 5, B). After that not much change could be noted, except 

 that the knobbed condition of the tentacles had disappeared, 

 until March 30. Then it was observed that a great amount of 

 the tentacles had been lost (Fig. 5, C). On March 31, but mere 

 stumps of the tentacles remained (Fig. 5, D}. The specimen on 

 April i, showed the bud of one tentacle making its appearance. 

 By April 8, tentacles relatively as long as those shown at A in 

 Fig. 5 were present. During the period of inanition the body, as 

 a whole, had been reduced in size so that by April 10 the re- 

 generated tentacles were relatively longer than those which were 

 involved at the beginning of the observation (Fig. 5, ). On 

 April 9, some parts of this second crop of tentacles had been 

 eaten. On April 14, the specimen died. 



In the above observations, no effort to control the factor, 

 presented by the accumulation of toxic metabolic products, was 

 made. It is quite possible that such effort need not have been 

 made, for the fed Hydras had grown in size and, therefore, must 

 have thrown a greater amount of toxic material into the water 

 than did the unfed specimens. In addition to this, the presence 

 of the Cyclops and daphnids added much to the concentration of 

 metabolic toxins in the water of the fed specimens as compared 



