GERM CELLS OF COELENTERATES 



35 



Table of measurements and computations of relative sizes of various coelenterate 

 eggs, and their nuclei. Diameters, in millimeters, are made from -projected 

 images of the eggs and nuclei; these multiplied by 1000 and divided by 137 will 

 give the diameters in microns. The diameters represent the average diameter of 

 the egg and nucleus, since often these are not perfectly spherical 



FORMS EXAMINED 



Starfish 



Nausithoe punctata. . . . 

 Hydractinia echinata. .. 



Pelagia noctiluca 



Obelia sp? 



Aglantha digitalis 



Campanularia flexuosa. 

 Gonothyraea loveni. . . . 



Aurelia flavidula 



Clava leptostyla 



Corymorpha pendula... 



Hydra sp? 



Eudendrium ramosum. . 



Pennaria tiarella 



Hybocodon prolifer 



Tubularia crocea 



DIAMETER EGG 



DIAMETER NUCLEUS VOLUME NUCLEUS 



2.0 



2.5 



2.555 



2.7272 



3.00 



3.0 



3.1428 



3.5 



3.6 



4.186 



6.583 

 6.714 

 7.875 

 9.848 

 14.625 

 18.166 



8.0 

 15.625 

 16.581 

 20.153 

 27.0 

 27.0 

 30.957 

 42.875 

 52.656 

 72.930 



284.848 

 302.6469 

 488.058 

 955.088 

 3122.794 

 5994.8435 



Very obviously the table is divided into two parts, 16 to 24 

 represent eggs with relatively large nuclei, and 25 to 30 have 

 distinctly smaller nuclei. Within each group there is a rather 

 marked gradation, but between the groups a noticeable gap. 

 The relation between the volumes of nuclei and cytoplasm may 

 be expressed in another way. In the first lot the egg volume 

 exceeds the nuclear volume by from 15 to 73 times, but the eggs 

 of the second group are from 284 to nearly 6000 times the volumes 

 of their nuclei. Each egg of the first lot obtains its nourishment 

 from the enteric ca\dty, from which it is separated by a single 

 layer of cells; the eggs of the second lot (except 27) absorb the 

 surrounding oocytes and ova and appear to depend upon these 

 almost entirely for their food supply. Eudendrium (27), in size 

 of nucleus, belongs to the second series, but does not absorb 

 oocytes; however, its gonophores are adapted to serve as nourish- 

 ing organs, and the cells of these are later absorbed, so it may 

 properly be placed in the second series instead of the first. 



