and Laboratory Methods. 1309 



method taken was to cut across with a small scalpel an individual in which the 

 normal fission plane had become well formed, at some other point of the body 

 than that at which the fission plane was appearing. It was found that when the 

 cut was anterior to the normal fission plane, the formation of this was inhibited 

 and the ganglionic masses which mark its position moved forward till they came 

 to the cut anterior end, where a head was formed. In other words, the tissue 

 which was to form a head migrated as a result of the operation to a position 

 where head tissue would normally never occur. When the cut was posterior to 

 the normal fission plane the latter was not inhibited, but the operation had a dis- 

 tinct retarding influence on its formation. The rule in this case appears to be 

 that the normal fission plane is not completely formed until the posterior piece 

 which has been cut away is wholly regenerated. 



In the theoretical discussion a comparison is made between the regulation 

 shown in this case and that of the blastomeres of the segmenting egg. It is 

 thought that the fundamental cause of the migration of the ganglionic cell mass 

 is to be found in the "-specific form of the animal,'' or, to quote the exact words-of 

 the authors : " We may conceive all the tissues of the individual animal to be in 

 a state, not of ^^?<!/-librium, but of Stenostoma-\\\iX\\mi ; and that when this is dis- 

 turbed in any way the whole system together tends to re-establish it ; and this 

 may be done through physico-chemical means.' 



The paper is one of great interest and suggests many possibilities. R. p. 



„..,,,, ^. ^ , T , • In these papers are given the results 



Qauie, J. Ueberden Einfluss der Jahreszeit i i o 



auf das Gewicht der Muskeln bei Froschen. of a Series of weighings of certam 



Arch. f. d. ges. Physiol. Bd. 83, p. 81, 82. muscles of frogs of both sexes, at dif- 



Taf. V, 1900. ^ • r 1 



Ueber die geschlechtliche Differenz der Mus- ferent seasons of the year. It IS found 



keln bei Froschen. Ibid. p. 83-88. Taf. ^^at during the summer while the 



V, 1900. ^ ,. 



frogs are feedmg the muscles take on 



weight, while in the winter months, when there is no feeding and the sexual pro- 

 ducts are being formed, the muscles lose weight. The muscle weight of the 

 males is at all times greater, per unit of body weight, than that of the females. 

 Physiological measurements were also made of the relative amounts of work 

 done by the isolated gastrocnemius muscles from the two sexes, when they were 

 put under the same experimental conditions and stimulated in the same way. 

 The results here show that the muscle of the male shortens more in contracting 

 than that of the female, but, on the other hand, the muscle from the female 

 raises a slightly greater weight than that of the male. The product gained by 

 multiplying the height through which the weight is raised by the amount of the 

 weight, gives a measure of the work done, and from determinations made in this 

 way it appears that the muscle of the male frog is capable of doing more work 

 than that of the female. The author believes that the material for the formation 

 of the sexual products is taken directly from the muscles where it has been 

 stored during the summer feeding season. These differences in the condition 

 of the muscles between the females and the males are thus thought to be due to 

 the greater amount of energy required in the forming of the sexual products in 

 one case, over that required in the other. R. p. 



