The early development of Eudendriiini. 261 



Reference was made in a preceding paragraph to the apparently 

 contradictory observations of Kleinenberg and Weismann. It seems 

 to me this may be rather apparent then real. In the first place 

 several species of Eudendrium so closely resemble each other at 

 certain stages of development as to render it easy to mistake the one 

 for the other. 



In the next place, there seems to have been assumed the inference 

 that the species of a given genus should have the same mode of 

 origin the sex-cells. This is clearly an unwarranted ^assumption as the 

 foregoing observations, as well as many others by various observers, 

 abundantly demonstrate. 



Kleinenberg's suggestion that the differences may be due in 

 some measure to seasonal conditions to which sexual processes may 

 be more or less responsive seems to be wholly inadequate as an ex- 

 planation. In the cases above cited, which were all obtained under 

 substantially identical circumstances and at approximately the same 

 season, it can, of course, have no significance. It would seem more 

 probable that there are undoubted variations in the same species 

 arising from intrinsic conditions of nutrition, or similar physiological 

 changes, and granted the fact of migration of these cells their response 

 to these changes is only what might be naturally expected. More- 

 over, it is not altogether improbable that such conditions of metabolism 

 might measureably influence the origin of the sexual products as well 

 as their development. 



Growth of the egg. in the Eudendridae. It is no longer 

 matter of doubt that the ova arise in these hydroids by differentiation 

 of cells of either one or both the entoderm and ectoderm. It may 

 be in the region of the hydranth or lower in the coenosarc of the 

 stem. When first distinguishable they are slightly larger than the 

 ordinary cells of the surrounding tissue, and differ also in shape,, 

 being generally ovoid or spherical and with comparatively conspicuous, 

 nuclei. Their form and size generally suffice to distinguish them from 

 the glandular cells often distinguishable in these hydroids, though in 

 their staining reactions they closely resemble the latter. Growth aÇ this 

 period would seem to take place in situ, through the direct nutritive 

 activity of the surrounding tissue cells. In texture the cytoplasm is 

 homogeneous, finely granular and with less staining avidity than the 

 nucleus, which from the first is large, with a prominent nucleolus and 

 with ready affinity for stains of almost any of the commoner sorts. 

 As growth continues the ova become more or less amoeboid, migrating 



17* 



