ANATOMY AND DEVELOPMENT OF HYDRA. 9 



find several new and important observations. When the 

 ovarium lias attained the development just described, a cell, 

 ■which usually lies almost exactly in the middle of the organ, 

 attracts attention by its rapid growth. This is the young 

 ejiff. It continues to increase in size and assumes a flattened 

 shape Avith irregularly-lobed margin. With further growth 

 it becomes divided by two deep indentations into two lateral 

 halves united to one another by a central isthmus in which 

 the nucleus (the germinal vesicle of the ovum) is imbedded. 

 This nucleus now begins to increase considerably in size, and 

 so also does the sharply-contoured nucleolus which is noticed 

 within it. The nucleolus, however, after it has attained a 

 certain size, disappears, and the nucleus now shows itself as a 

 sharply, double-contoured vesicle filled with a very finely 

 granular, weakly refringent mass. 



The egg continues to increase in width, and the irregular 

 lobes of its margin become more strongly developed. Its 

 shape in this state with its two large, flat lobes and their 

 connecting isthmus, is compared by Kleinenberg to that of a 

 butterfly Avith its wings expanded and torn at their edges. 

 In the germinal vesicle there now appears close under its 

 membrane a clear, circular, flat body, the germinal spot. 



In Hydra viridis chlorophyll granules now become deve- 

 loped in the egg, both in its central parts and in its peripheral 

 lobes. As we know chlorophyll to be in Hydra a product of 

 the endoderm, the ectoderm being entirely free from it, we 

 are called upon to reconcile this fact with its appearance in 

 the egg, which, according to Kleinenberg, is exclusively de- 

 rived from the ectoderm. Our author anticipates this objec- 

 tion, and dismisses it with the remark that it only shows that 

 the egg long before the occurrence of fecundation has liberated 

 itself from the physiological tradition of the tissue in which 

 it had its origin. 



The marginal lobes and processes of the egg now greatly 

 increase in size, extend farther from the central protoplasm, 

 become dichotomously branched, and form, in fact, the principal 

 part of the egg. The shape of the egg thus becomes remark- 

 ably different from the ordinary one, and is stated by Kleinen- 

 berg to be '^exquisitely amoebiform." 



I can fully confirm Kleinenberg's statement of the irregu- 

 larly-lobed condition of the egg in this stage, having, some 

 years ago, noticed it very distinctly in H. vidgaris, but I feel 

 very doubtful as to the propriety of designating this condition 

 as amoebiform, a term which may tend to give an incorrect 

 impression, as the processes cannot be regarded in the light 

 of protrusible and retractile pseudopodia, 



