1902.] NATURAL SCIENCES OF PHILADELPHIA. 765 



length by Yerkes,^ His account would apply almost as well to the 

 process in the hydra. The tentacle which comes in contact with the 

 prey is contracted with a suddenness and vigor which belies the ap- 

 parent inertia of the moment before. The victim is seen to be firmly 

 spitted on the microscopic lances of the nematocysts, and it is evident 

 that the first thing that happened when the animal touched the 

 tentacle was the discharge of all the thread cells in that region. 

 The tentacle in contracting carries the food, protozoan or minute 

 worm, or whatevei', toward the mouth. The long manubrium then 

 moves about slightly as if in search of the morsel. Finally the 

 tentacle places the food directly upon the mouth (PI, XXXII, fig, 

 16), which proceeds to turn itself over the object and work it down- 

 ward until it vanishes into the gastric pouch of the polyp. 



Degeneration Phenomena.^ 



For some reason or other, not understood at present, the larvae 

 in one of my aquarium jars began when three months old to 

 exhibit most singular forms and activities. All appearance of the 

 hydra form was lost, ectoderm and endoderm becoming indistin- 

 guishable and cell outlines dissolved. The larva in this condition 

 had very much the appearance of an amoeba, Tlie specimens 

 slumped down on the bottom of the aquarium in a shapeless mass, 

 and by protoplasmic flowing changed their shape through an end- 

 less variety of forms, moving slowly from point to point. Thin 

 l^seudopodia were sent out, along which the substance of the organ- 

 ism flowed, and by the breaking of the connecting isthmus divided 

 into two. Thti fragments became smaller and smaller until no 

 longer recognizable. These abnormal larvae remained alive for six 

 weeks, after which no trace of them was to be seen. 



Budding in the Larv.e — jMetagenesis." 



Contrary to Haeckel's statement that in the group of jelly-fish 

 which he calls the " Trachomedusse " metagenesis does not occur, in 



' R. M. Yerkes, "The Sensory Reactious of Gonioncmus," Am. Journ. 

 Physiology, February, 1903. 



* More fully described iu the Biological Bulletin of the Marine Biologi- 

 cal Laboratory, Woods Hole, August, 1902. 



" An earlier draft of this section appeared iu the Johns Hopkins Univer- 

 sity Circulars, June, 1903. 



