1897.] Embryology. 83 
Kealing Island. “The insects were observed at night and during heavy 
rain, suggesting nocturnal migration with the possibility that they were 
seeking shelter from the rain, or were attracted by lights in the cabin. 
This power of extended migration will also account for the extension 
of the species over the whole intertropical zone, and far beyond it on 
either side, 
EMBRYOLOGY!’ 
Movements of Blastomeres.—In a lengthy and detailed paper 
Professor Roux? gives the! results of certain experiments upon the 
isolated cells of the morulas and young gastrulas of the frog. In pre- 
vious papers he had shown that when the cells are teased apart in solu- 
tions of salt or of white of egg they may move together again, travers- 
ing short distances without any apparent means. He considered that 
cells aitracted one another somewhat as do sperm and ovum and rele- 
gated such attractive phenomena to the field of chemical influences. 
In the present paper minute and rigorously classified descriptions 
are given of changes which such cells undergo when once they have 
come into contact. 
In general two or more cells in contact glide, or crawl as it were, upon 
one another into some new relative position. This movement of one or 
both may be accompanied by a revolving or waltzing, very slowly. The 
form of the cells becomes changed very markedly, as is especially well 
shown when three cells form a row. In this case the middle one is 
very much compressed, as if the cells crowded together with great force. 
The rearrangements and changes of shape are in some cases much as 
take place with soap bubbles and might be explained as the resultant 
of the surface tensions of the separate bubbles or cells. But in many 
cases the arrangements are directly opposed to the laws governing the 
arrangements of soap bubbles and cannot be explained on so simple a 
asis. 
Besides the external changes in form and position there are internal 
changes, as is made evident by the changes in position of the pigment, 
In such cells as have more or less pigment this may recede from the 
Surface to appear again in concentrated form at some one region of the 
i Edited by E. A. aremt Baltimore, Md., to whom abstracts reviews and 
preliminary notes may be se 
? Archiv f. erep d. Org., TET June 12, 1896, pps. 381-464. 
