432 The American Naturalist. [May, 
and the different results depend on agencies outside the developing 
cells. This he applies to the regeneration of lost parts in Obelia, by 
by cutting off the hydranths and their stalks at different levels. His 
conclusions are: 
“First. The regenerative tissue is not differentiated at different 
levels to produce different things independent of environment; but on 
the contrary, the embryonic tissue at all levels may produce the same 
things. 
“Second. Wholly aside from the production of definite things, there 
may be acquired in certain embryonic tissues a usual method of devel 
opment, independent of environment. * * ` 
“Third. The curves of regeneration bring out a second wholly 
unexpected series of facts; namely, the tendency of regenerative tis 
sue at all levels to produce preferably certain forms. * * * ” 
Closely allied to these observations of Davenport are some by 
- Albert Lang’ who, working under the direction of Professor Weismann, 
claims that in certain hydroids, notably in Hydra, Eudendrium and 
Plumularia, both germ layers do not participate in the formation of the 
buds but that these structures proceed from the ectoderm alone w 
by asort of multipolar gastrulation forms the entoderm of the bud, 
and is to be regarded as the sole foundation of the daughter individ- 
ual. Accompanying this paper is a note by Prof. Weismann stating 
that the facts observed by Lang were just such as he had predicted 
upon theoretical grounds. 
Shortly after the publication of Lang’s results, his experiments r 
gone over by an American student who found that while he cou 
easily duplicate Lang’s figures, the conclusions based upon them bes 
due to errors of misinterpretation and that in reality both layers i 
participate in the bud formation. These results have not been p" 
lished. This is, however, the less to be regretted since Dr. F. Broen 
of Breslau has recently gone over the whole matter and he anoni 
that Lang’s account is all wrong. He finds nothing which ae 
port Lang’s conclusions, there is no fusion of one germ layer W! 
other and never a proliferation of cells of the ectoderm of sa 
to form the entoderm of the adult. 
the 
The Parietal Eyes.—Those who have kept close igor E 
progress of our knowledge of the “pineal gland” can p and by 
ested in some recent papers. Long believed to be a gland 
*Zeitsch. f. wiss, Zool, LIV, 365, 1892. 
‘Biol. Cblt. XIV, 140, 1894. 
