1888.] MICKOSCOPICAL JOURNAL. 209 



problem was to detei'mine the relationship of Hydrichthys from a study of 

 the medusa alone, we could easily conclude that it is a near relative of Sarsia. 

 Such a conclusion is one that can easily be defended. When, however, we 

 come to compare the hydroid of Sarsia and the hydroid of Hydrichthys, we 

 find the greatest differences between the two. These differences are so impor- 

 tant that they have affected the whole structure ; for a comparison of the two 

 reveals the effect of the peculiar mode of life in Hydrichthys. The typical 

 structure, or schema, of the tubularian hydroid, as Coryne, is a slender axis 

 which may be naked or encased in a chitinous tube, an enlargement at the 

 free end, and a terminal mouth opening. This mouth opening or the walls 

 of the enlargement bear tentacles in rows irregular or otherwise. Some- 

 where among these tentacles, or elsewhere on the stem, arise buds which may 

 or may not develop into medusas. The widest variations from such a sche- 

 matic type might be noticed among hydroids. Our purpose here is to com' 

 pare Hydrichthys with the so-called schema. 



In the case of the gonosome of Hydrichthys I suppose that the stem of the 

 schema remains, that the terminal mouth opening is present, but that the 

 enlargement of the axis has disappeared. From the sides of the axis arise 

 lateral branches as in some hydroids and the medusa buds have been crowded 

 to the distal ends of these branches. Tentacles have disappeared on account 

 of the parasitic nature of the life of the hydroid. It is from this fact that 

 we find in Hydrichthys the schema of the ordinary tubularian hydroid re- 

 duced to a simple sexual body or gonosome. 



In the homology of the ' filiform bodies ' of Hydrichth3'S the reduction, as 

 compared with the schema of a hydroid, has gone still further on account of 

 the parasitic life, and nothing remains but a simple axis without appendages 

 of any kind. 



If I am right in this homology of the two kinds of individvials in the 

 Hydrichthys colony, it would seem as if there ought to be a meaning for 

 their simple structure as compared with the typical hydroid. The relation 

 of the medusa to that of Sarsia-like genera would imply degeneration, not 

 phylogenetic simplicity. Cannot we find in parasitism a cause for such 

 a degradation ? 



Is the conclusion legitimate that these great differences between Hydrich- 

 thys and the fixed hydroid closely related to it are the result of its peculiar 

 mode of life? I believe it is. I believe that the modification in the hydroid 

 Hydrichthys, the loss of tentacles, the polymorphism, and the increase in 

 prominence of the sexual bodies, are exactly what we should expect to find 

 a priori if a degradation had taken place in its structure. 



The Seat of Formative and Regenerative Energy.* 



By C. O. whitman. 



The question of the role of cytoplasmf is twofold. Is it merely passive 

 and wholly at the mercy of forces either external or emanating from the 

 nucleus, or is it self-active, automatic as well as acted upon ? 



A strong tendency now exists to refer all the changes in the cytoplasm to 

 the agency of the nucleus. The purpose of the pi'esent article is to consider 

 the regenerative and formative powers of the cell whether residing in the 

 nucleus or in the cytoplasm, or in both, as a physiological unit. 



* Condensed from original article in The Journal of Morphology, vol. ii, part i, p. 27. 

 t Cytoplasm is defined as the protoplasm of the cell exclusive of the nucleus. 



