1884.) Zhe Larval Theory of the Origin of Cellular Tissue. 463 
even think of the supporting zodns, which represent the inclosed’ 
mesoderm of Metazoa, as resting on the ground. The inclo- 
sure might have been simply due to concentration in the larve 
of descendant forms, which connected them with the Meta- 
zoa, since this would be a natural sequence of inheritance with 
concentration of the secondary formation of the mesoderm. 
Of course this picture can only indicate what seems to us the 
probable course of the morphology, and also our disposition to- 
regard as unfounded all hypotheses which have asserted that es- 
sential structural characters originate, as a rule, in larval stages, 
or are likely to occur without being derived through inherited’ 
concentration of characteristics from former generations. Simul- 
taneously with the differentiation of supporting or mesodermic 
zoons, we should also expect to find male and female zoöns aris- 
ing, if the results of investigations among sponges mean any- 
thing, from among the Supporting zoons, or becoming, at least. 
in the immediate transitional forms, confined to this layer.) 
It is not of course necessary to this hypothesis that no other 
transitional forms occurred leading to other types of Metazoa, or 
that all reproductive zoons originated in the mesoderm. As larval 
d the Spermatocysts would inherit the tendencies to sponta- 
neous fission of the nucleus at earlier stages in the successive forms, 
and the resulting cells or fertilizing elements would acquire the 
Pe and the habits of the full-grown ancestors, if they also- 
larval forms. The parallel between the encystment of the 
a “‘matocyst in the sponge tissue, and of the adult among Pro- 
takes <a ated similar. The process of spontaneous fission 
Place in both bodies in similar way after their encystment. 
— the above was wri 
‘St, 1884, in which Bü 
and female zoéns as individuals, and that the male pro- 
ale. Thus which, like spermatozoa, seek out and fertilize 
females. nS Bütschli has discovered the intermediate forms with males and 
ypoth 
tten we have received Biologisches Centralblatt for 
iin “i may add, in Vorticella. We cannot, however, at all join 
aires respectively mb Spermatocyst and the ovum as the morphological represent- 
om ue exclusive male colonies and female colonies of some 
F Mal, either male P This would be assuming every cell to be primarily unisex- 
-i ae primarily sexic« pone, our standpoint being with Minot and Balfour, that they 
3 Mependenit differeryiat a y that is hermaphrodites, and the sexes the result of 
e ' on, 
