EARLY DEVELOPMENT OF HYDRA. 21 



There is a definite nuclear membrane closely applied to the 

 cytoplasm. 



In some cases a single cross-section has shown three eggs 

 almost fully grown. Their separate masses in such cases are not 

 separated by an egg membrane of any sort, but flow into each 

 other at their boundaries, which are indicated by a lesser thick- 

 ening of the egg mass. In such cases it appears that there are 

 three distinct areas in which the growth of an egg has begun in 

 the manner previously described. Tannreuther ('o8) has made the 

 observation that after the coalescence of the large ova, two or 

 more of the nuclei persist and each becomes a functioning nucleus, 

 and each, presumably, appropriating a portion of the original 

 mass making up the cytoplasmic portion of the growing egg or 

 eggs. My observations have given no evidences of such a condi- 

 tion or process, but indicate rather that egg development begins 

 in two or more points or areas, and growth continues, until, by the 

 total appropriation of the nourishing cells, their masses become 

 continuous. 



By the time the egg has attained its growth the nucleus has 

 migrated to the periphery of the egg where it lies in an area free 

 from pseudo-cells, and just beneath the ectoderm. The mem- 

 brane becomes very indistinct, while a slight shrinkage away from 

 the cytoplasm is noticeable (Fig. 14, PI. II.). This condition 

 becomes more pronounced for the outline of the nucleus becomes 

 very irregular and almost indistinguishable. This condition, as 

 Brauer {'gia) has stated, precedes the formation of the first 

 maturation spindle. 



Maturation. 



These processes have been described by Brauer ('gia) and Tann- 

 reuther ('08) for Hydra sp. ?, and my own observations have added 

 little to the account as given by them. The former writer 

 states that the number of chromosomes is probably twelve or 

 fourteen. Their shape and size make an accurate determination 

 difficult, but I am inclined to consider that the number is as great 

 as sixteen. The polar bodies are easily found in mature eggs, 

 lying just beneath the ectoderm, and may remain attached to the 

 egg by a cytoplasmic strand even after exposed to the water. 



