6o (124) Society for Experimental Biology and Medicine. 



(the embryo in a narrower sense), appear over the lower, or yolk 

 hemisphere of the egg. 



26 (72). " Rejuvenescence in protozoa " : GARY N. CALKINS. 



The process of conjugation in protozoa involves either tempor- 

 ary or permanent union of two individuals. During this union 

 there is a fusion of nuclear material from both organisms resulting 

 in the formation of new cleavage nuclei in each exconjugant. The 

 process is directly comparable with fertilization of an egg by a 

 spermatozoon, and the biological significance of the phenomena 

 involved is probably identical in all living things. 



Since 1876 it has been generally assumed that one effect of 

 conjugation is rejuvenescence or renewal of vitality in both of the 

 exconjugants. This assumption has never been submitted to 

 experimental proof. In his Paramecium work, begun in 1901, the 

 author almost had the proof, but allowed the opportunity for 

 obtaining it to slip through his fingers without realizing its impor- 

 tance at the time. The author's object in bringing this up at the 

 present time is to announce that on the last day of February (1905) 

 he started a new series of experiments with Paramecium, consisting 

 of three different lines at present in about the fortieth generation 

 after conjugation, mainly for the purpose of completing his earlier 

 work. 



Another point of general biological importance will also be 

 investigated. In his original experiments the author found strong 

 evidence that the old view that both exconjugants are rejuvenated 

 is erroneous. In twenty pairs which were cultivated after separat- 

 ing from conjugation, one individual of each pair invariably out- 

 lived the other, thus indicating an incipient fertilization like that in 

 metazoa. This phenomenon will be given careful study in the 

 experiments now under way. 



27 (73). " Temperature and muscle fatigue " : FREDERIC S. 

 LEE. 



It has been pointed out previously by the author and others 

 that the contraction process of the muscles of cold-blooded animals 

 in the course of fatigue becomes greatly slowed, while those of 

 warm-blooded animals show no such phenomenon. Lohmann 

 has recently claimed that a cold-blooded muscle on being heated 



