262 CHAS. W. HARGITT, 



toward the gonophore region where they seem to aggregate in con- 

 siderable numbers, the presence of which may act as a stimulus from 

 which results the formation of the gonophore. These organs may arise 

 singly or several may arise in close connection forming clusters, into 

 which the ova readily migrate. Almost immediately following their 

 final position in the gonad a change becomes apparent in the character 

 of the cytoplasm of the egg. It loses its finely granular and homo- 

 geneous character and acquires a store of deutoplasm which assumes 

 the form and special characters of yolk spheres. 



These first appear about the periphery of the egg and are of 

 large size. As they accumulate by the constant formation of new 

 spheres within the cytoplasm of this region they become massed toward 

 the center of the egg, thus crowding the cytoplasm toward the sur- 

 face. Indeed it may not be improbable that during this period there 

 may exist more or less active cytoplasmic movements which are 

 effective in the final disposition of the egg contents. This is further 

 suggested by the gradual change of position by the nucleus in the 

 later phases of growth and approaching maturation, as shown in 

 Figs. 5—7. It should not be overlooked however, that the nucleus 

 may possess intrinsic powers of migration in these eggs, as strongly 

 implied in the pseudopodial processes found in many cases, as shown 

 in Fig. 6. 



That the yolk spheres arise directly through the cytoplasmic 

 activity of the egg there can hardly be any doubt, tho their substance 

 comes indirectly from the metabolism of the entodermal layers of the 

 gonophores, which with the growth of the egg is gradually reduced 

 in mass till its cellular character is almost or wholly lost. 



Various phases in this line of metabolism are easily traced in 

 hydroids with fixed gonophores but it is unnecessary to submit details 

 in this connection. 



As these yolk masses increase a change takes place in the 

 character and position of the nucleus. It no longer occupies the 

 center of the egg but migrates toward the periphery, or it may be 

 that the increase of food spheres which aggregate in the center of 

 the egg forces the nucleus into an eccentric position, along with the 

 cytoplasm which likewise becomes more or less peripherally disposed. 

 Change of position is not however the most important which 

 overtakes the nucleus during this period of the growth of the egg. 

 Changes of texture of the nucleus become more or less apparent 

 both in living eggs and in the reactions shown by staining agents. 



