636 J. T. PATTERSON 



coelenterates, ascidians, and Polyzoa the germ cells antedate the 

 formation of the buds in which they are found; and Montgomery 

 ('06) has gone so far as to suggest that perhaps in all cases the 

 products of asexual reproduction contain germ cells. He sug- 

 gests that "If this were so, it might then be the case that the 

 incapacity of any part of the body of an animal to reproduce 

 asexually or even to regenerate, would be due to the absence of 

 germ cells in it. " It may be possible to explain in this way the 

 appearance of rudimentary embryos that have been observed in 

 both species of armadillo, or even, indeed, to account for the o- 

 called asexual larvae in Litomastix. Such abortive attempts to 

 produce normal organisms may be the result of a failure on the 

 part of a bud to receive germ cells. 



2. Origin of polyembryony in the Dasypodidae 



One of the interesting problems which presents itself in con- 

 nection with this study pertains to the question of the origin of 

 specific polyembryony among the Dasypodidae. The question 

 becomes all the more interesting, from the standpoint of the physi- 

 ology of reproduction, in view of the fact that the uterus of the 

 armadillo is of the simplex type. The same type of uterus in 

 other mammals is adapted to the function of receiving and nour- 

 ishing a single ovum, although occasionally it may receive and 

 nourish two or more ova at the same time, in which event a multi- 

 ple birth results ('frajternal twins/ 'triplets/ etc.). In the arma- 

 dillo the uterus also receives a single ovum at a time, but instead 

 of but one embryo arising from the egg, polyembryonic develop- 

 ment comes on and increases the number of offspring to several 

 individuals. Here we have a clear case of adaptation, in which 

 the productivity of the ovum of a uniparous mammal is increased 

 several fold. 



Two quite distinct problems are presented. One of these is the 

 most fundamental question of the whole problem of polyembry- 

 ony, namely: What are the causal factors underlying the forma- 

 tion of two or more individuals from a single egg? The other 

 problem concerns the phylogeny of specific polyembryony in 



