12 GEORGE T. HARGITT 



Growth of egg cells. Whatever may be the origin of the egg, it 

 Hes for the entire early period of its growth within the entoderm. 

 An explanation for this is obvious, in such a position the egg is 

 very close to the enteric canal with its circulating fluid from which 

 the nutrient material is obtained for growth and for elaboration 

 of reserve stuffs. Figures 3, 4, and 6 to 9, show the relation of 

 growing eggs to the entoderm and enteric canal. Since the egg 

 does not come into contact directly with the enteric cavity — - 

 entoderm cells always being interposed — it seems probable that 

 these entoderm cells aid in nourishing the egg. After the oocyte 

 or young egg is formed and before it has begun to grow to any 

 marked extent, it has the structure already described, viz., com- 

 pact, granular, deeply staining cytoplasm with a large nucleus 

 and nucleolus (figs. 7 and 8). 



In the egg which has started its growth or in which a period 

 of rapid growth is just initiated certain changes become notice- 

 able; these are illustrated in figures 9 to 13, which represent a 

 series of eggs of different stages of growth, all from the same 

 general region of one colony. The eggs represented in figures 9 

 and 10 are from the stem of the hydroid close to a lateral branch 

 which bears gonophores ; they are just entering upon the period of 

 rapid growth. The chromatin of their nuclei is in a more ob- 

 vious network, the nucleolus more or less vacuolated, but some- 

 times homogeneous and without vacuoles (fig. 10), the cytoplasm 

 not so dense as formerly, but still not alveolar, without yolk, 

 but containing a scattered lot of prominent and intensely stain- 

 ing bodies. These bodies are of nuclear origin and are similar 

 to the granules found in the cytoplasm of Clava, Campanularia, 

 and Aglantha, which were derived from the chromatin of the 

 nucleus. 



While the egg is small these bodies are more or less scattered 

 through the entire mass of the cytoplasm. When growth is 

 well under way and proceeding rapidly, this extranuclear chro- 

 matin is massed close to the nucleus (fig. 11) and does not ex- 

 tend far into the cell body. This may indicate a rapid absorp- 

 tion of the material by the cytoplasm. The cytoplasm at such 

 a period is more loosely arranged and shows a beginning of an 



