CYTOLOGY OF THE MYXOMYCETES. 87 



they are identical in animals and in plants. Champy's ('n, p. 

 154) statement that "I would not regard as living a cytoplasm 

 which does not contain mitochondria" is rather radical in view 

 of our knowledge of the structure of the lowest plants. The 

 bacteria and the Cyanophycese are of special interest in this con- 

 nection. Furthermore, it is common to find comparatively 

 large stretches of protoplasm in certain of the Myxomycetes 

 which contain no mitochondria. While we cannot say how active 

 this protoplasm is we cannot regard it as totally inert and life- 

 less. 



Concerning the continuity of mitochondria in the Myxomy- 

 cetes it may be said that they invariably occur in the plasmodia 

 as well as in all stages of spore formation, even to the adult spore. 

 While I have not yet studied the swarm spores, it is extremely 

 probable that mitochondria occur in all stages of the life cycle. 

 No indications were observed of de novo formation of mitochon- 

 dria though it is highly improbable that if such occurred they 

 would have been detected. It seems unnecessary to assume, 

 as some workers have done, that we must find mitochondria 

 grading into the invisible in order to demonstrate a de novo 

 origin, because it is possible that the mitochondrial aggregate 

 must attain to a certain size before acquiring characteristic 

 density and staining reactions. 



The cyclical changes in the morphology of the mitochondria 

 suggest similar changes which have already been described, long 

 since, in higher forms. The most striking of these is the change 

 from the large spherical mitochondria of the youngest spores to 

 the smaller rather rod-like ones of those which are more mature. 

 They resume their granular condition in the mature spores. 

 They are often rod-like and arranged parallel to the direction of 

 the current in streaming protoplasm of active plasmodia. Their 

 clumping about the nucleus and their whole behavior make it 

 very plain that their morphology and distribution are governed 

 by the same laws here which operate in animals and in the higher 

 plants, whatsoever they may be. 



It is interesting to note, a propos of current statements to the 

 effect that the mitochondria are transformed into cellular dif- 

 ferentiations, that, so far as can be ascertained, they play no 



