0^ ZOOLdClY ORGANlSAtiOif, 82/ 



S^cdtlaucl. The meeting was attended by twenty-one persons. A vote of 

 thanks to the Royal Society of Edinburgh for the loan of the Society's 

 rooms for the purpose of the meeting was passed. 

 The Committee ask to be reappointed. 



The Injlmnce of Salt and oilier SaUdion^- ok, the Decelopment oj the 

 Frog. — liepori of the Commiitee^ consisliivj of Professor G. C 

 BoURxXE (Chairman), Mr. J. W. Jenkinson (Secretarij), and 

 Professor iS. J. HlCKSOiX. {Drawn up hij the Secretanj.) 



I. On the Efcct of certain ,'<olutioyis upon the Developiivj Egg. 



A. As has been set forth iu previous reports, the solutions employed 

 may be t'lassitied, according to the effects they produce, as follows :— - 



i. Those which kill the bgg in an eaily stage (segmentation or 

 gastrulation) ; e.g., NHjIjCaCl... 



ii. Those which kill the egg during the formation of the medullary 

 folds ; e.g., NaT. 



iii. Solutions which allow development to proceed but disturb it — 



(a) The embryo remains more or less spherical. The medullary 

 groove usually remains open, the yolk-plug usually persists ; e.g., LiCl, KCl, 

 (/3) The embryo elongates ; differentiation is greater than before. 



1. Blastopore and medullary groove remain open ; e.g., NaCljK^SO^. 

 '1. The blastopore closes, the medullary folds remain wholly or partly 

 open. 



Cane sugar and magnesium salts. 



iv. In dextrose development is retarded, but is normal in form. 



V. Solutions in which development is normal both in form and rate. 



(<i) In urea the tadpoles die. 



(/3) In Na2S04 they remain alive. 



13. It was also pointed out — 



1. That these diverse effects cannot possibly all be due to the increased 

 osmotic pressure of the medium, and to that alone ; 



2. But that the part conceivably played by the osmotic pressure in 

 any particular case cannot be determined until the permeability of the 

 tissues of the embryo to the substance is known. 



3. That since Davenport has shown that the tadpoles absorb water at 

 a very rapid rate, they are presumably very sensitive to a loss of water, 

 and hence a means is afforded, by observing the effect of tliese solutions 

 upon the tadpole, of ascertaining the permeability of the tadpole, and so, 

 indirectly, of the egg and embryo, to the substances employed. 



C. It was then shown that the tissues of the tadpole are permeable to 

 urea and NaoSOj, more or less impermeable to cane sugar and NaCl, and 

 more to the former than to the latter. 



During the present year this experiment has been continued, and it 

 ha.s been demonstrated that the tadpoles are permeable to the magnesium 

 salts, more or less impermeable to dextrose, but not quite so impermeable 

 as to NaCl. 



