EARLY DEVELOPMENT OF HYDRA. 5 



the cells divide after reaching this stage, is rather uncertain. In 

 none of the sections examined were there found conclusive evi- 

 dences of such divisions taking place either mitotically or amitoti- 

 cally. There were present, however, many cases in which a cell 

 was possessed of two nuclei. It was thought at first that division 

 took place amitotically, for some of the nuclei were markedly 

 elongated, and might easily give foundation for such belief. 

 Such doubly nucleated cells probably arise from the coalescence 

 of two cells. 



The two nucleoli, above referred to as frequently being present 

 in the nucleus, are not chemically the same, as they differ in their 

 staining reaction, one staining much more deeply than the other 

 (Fig. I, PI. I.). In some cases each of the nucleoli is found to 

 be made up of two parts, in which again, one differs from the 

 other in staining reaction. One appears to be a true nucleolus, 

 while the other probably consists of a droplet of some food ele- 

 ment passed through the nuclear membrane. Darkly staining 

 bodies are also found in the meshwork of the cytoplasm (Fig. i, 

 PI. I.). These appear to be true metaplasmic bodies, probably 

 food material taken up by the cell. They are not found in all 

 cases, and their pi'esence is probably dependent upon the physio- 

 logical activities of the cell. Frequently, the nucleolus migrates 

 out of the nucleus by rupturing the nuclear membrane (Fig. 6, 

 PI. I.). The nucleolus is usually surrounded by a clear non- 

 staining area. The chromatin material forms a fine network often 

 somewhat peripherally arranged. In especially well-stained prep- 

 arations one can distinguish very delicate threads which appa- 

 rently hold the nucleolus in position. The nuclei themselves are 

 either round or ellipsoidal in section. In the former case but one 

 nucleolus is present, in the latter, two (Fig. i, PI. I.). Doflein 

 ('97) describes similar conditions in the primitive ova of Tubularia 

 mesembryanthefnum, and Allen ('00) for T. crocea. 



In the nests of interstitial cells from which the primitive ova 

 are derived, one usually finds nematocysts developing in large 

 numbers. In the course of development of the ovarian area 

 these nematocysts either migrate out, or are resorbed. Fre- 

 quently they are found within the ^^^ itself. 



