1/4 IIKNRV FARNHAM PERKINS. 



A degenerate condition which is by far more striking and 

 significant was observed in the case of individual polyps, 

 which underwent fundamental changes of a remarkable char- 

 acter. The polyps in which these phenomena appeared were 

 reared in the laboratory from eggs laid in August, 1901, at 

 Woods Holl. Several lots of larvae were reared in aquarium 

 jars, some living for several months, others dying and quickly 

 vanishing after a few weeks. Only one jar of larvae exhibited 

 the peculiar forms which are described in this paper. In all 

 the jars, as nearly as possible, the natural conditions of the 

 larvae were imitated by keeping fresh algae, ulva, diatoms, etc., in 

 the water with the creatures. Some of the jars of polyps were 

 left at Woods Holl for three months, and then forwarded to the 

 zoological laboratory at Baltimore. These were found to con- 

 tain healthy larvae, which remained alive until February. But 

 one of the jars, instead of remaining at Woods Holl for the 

 balance of the summer, was taken directly to the laboratory, and 

 the contents were frequently examined. About the first of 

 October, the amoeba-like forms were first seen. For some time 

 no attention was paid to them, as they' were simply taken for 

 amoebae which had been introduced with the sea water. But it 

 was soon seen that the number of healthy polyps was rapidly 

 diminishing, while the supposed amcebae were becoming sur- 

 prisingly numerous. More careful attention was then paid to the 

 creatures, and it was discovered that the polyps were undergoing 

 remarkable changes. Single individuals were noted from time 

 to time, and observed to contract, first losing the Hydra-\\ke 

 aspect, the tentacles being completely retracted. The upright 

 body of the polyp then settled down upon the glass, and all 

 semblance of its natural shape was completely lost. - Moreover, 

 the differentiation between ectoderm a'nd endoderm could no 

 longer be discerned, except dimly in a few instances (T, Fig. 4). 

 The cell-walls lost their distinctness and soon disappeared. In 

 this remarkable way the originally vigorous hydra, standing up- 

 right with mouth gaping and tentacles widely extended, became 

 quickly degenerated into a shapeless mass of substance without 

 organs, only sluggishly motile, without discernible cell-bound- 

 aries or tissue layers, in short, an organism which was hardly 

 more than a plasmodium. 



