Maech 10, 1911] 



SCIENCE 



391 



and small cell aggregates fuse and give rise to 

 lumps, which become smooth and secrete a peri- 

 sarc. Their size and shape are within control. 

 Such bodies are solid masses in which cell limits 

 exist, although the structure may be in part 

 syncytial. They show at first but little change 

 and are subject to great mortality. After two or 

 three days many throw out one or more cylin- 

 drical outgrowths in which ectoderm and ento- 

 derm are dififerentiated. In the case of some of 

 these, growth and differentiation continue until 

 the end of the outgrowth is transformed into a 

 perfect hydranth. 



Masses resembling those just described were 

 obtained in a similar way from an aleyonarian, 

 Leptogorgia, and when the immature gonad of 

 Asterias was broken up, the cells quickly fused, 

 forming lumps and plates. Probably the power 

 to fuse resident in the cells and cell aggregates 

 into which a body (in the case of lower meta- 

 zoan) or tissue (in ease of higher form) may be 

 broken up, is wide spread. What degrees of re- 

 generative power may be resident in such masses 

 is a matter for investigation. (Paper to appear 

 in the Journal of Experimental /^oology.) 



The Prollem of Form in Hydra: Hebbebt W. 



Rand, Harvard University. 



In the problem of form as presented in onto- 

 genesis we have progressed so far as to be able to 

 state confidently that the essential form-deter- 

 mining factors are within the organism itself. 

 We must now discover to what extent and where 

 in the organism these formative agencies are local- 

 ized. The line of attack upon this problem lies in 

 experiments involving various derangements of 

 the normal form of relatively simple organisms. 

 The available morphogenetic data upon Hydra 

 probably exceed in quantity and diversity those 

 upon any other equally simple organism. 



An examination of the total evidence afforded 

 by Hydra leads to the conclusion that in the 

 normal adult the peristome is the seat of some 

 peculiarity by virtue of which that region exer- 

 cises formative control over column substance, 

 whether it be substance of the column to which 

 the peristome originally belonged, or of any other 

 column with which the peristome material comes 

 into relation by transplantation. When a piece 

 of column regenerates a head, this form-control- 

 ling condition is established in the prospective 

 peristome material in advance of the visible for- 

 mation of oral organs and as a prerequisite of it 

 (Browne, 1909). This localizing of the formative 

 agencies is a function of the whole of the regen- 



erating piece. In the normal hydra, therefore, 

 heads are not, in any direct sense, preformed at 

 various levels of the column. 



In graft-compounds having two or more heads, 

 the regulatory changes may, without exception, 

 be interpreted as dependent upon competition of 

 the several peristomes for control of the column 

 substance. 



The phenomena of regeneration and regulation 

 fairly compel the assumption of the existence of a 

 specific formative force-system for which those 

 particular chemical complexes which constitute 

 hydra substance serve as the vehicle; and, to- 

 gether with the phenomena of polarity, they afford 

 ground for some conception of the distribution 

 and mode of operation of such a force-system. 

 (A full treatment of the subject is being prepared 

 for publication.) 



The Proportion of Male-producers in Hydatina 

 senta as Affected hy External and Internal 

 Factors: A. Franklin Shiill, Columbia Uni- 

 versity. 



The proportion of male-producers in the rotifer 

 Hydatina senta can be reduced by rearing the 

 animals in weak solutions of urea, several am- 

 monium compounds, beef extract or creatin. 

 Since some of these substances exist in the food 

 cultures used in the experiments, starvation may 

 appear to increase the proportion of male-pro- 

 ducers because smaller quantities of these sub- 

 stances are administered with the food. 



Different pure lines of rotifers obtained from 

 widely separated localities yielded different pro- 

 portions of male-producers when reared under the 

 same conditions; this indicates the existence of an 

 internal factor that plays a role in determining 

 the proportion of male-producers. When indi- 

 viduals belonging to distinct pure lines were 

 crossed, the offspring gave rise to pure lines (Fi) 

 yielding morj male-producers than either parent 

 line. When a member of one of these Fi lines 

 was crossed with an individual from one of the 

 parent lines, the zygote gave rise to a line (F™) 

 producing a proportion of male-producers inter- 

 mediate between those of its two parent lines. 

 The explanation of these results is not yet clear. 

 (To be published in the Journal of Experimental 

 Zoology. ) 



Evolution of Hectocotylism among Cephalopods: 

 G. A. Deew, University of Maine. 

 The paper read will be included in a paper 

 bearing the following title : " Sexual Activities of 

 the Squid, Loligo pealii (Les.) — 1. Copulation, 

 Egg-laying and Fertilization." It is to be pub- 



