GENERATION OF ANIMALS, IV. iv.-v. 



residue) of the solid nourishment was grown to- 

 gether ; in fact, in Perinthus a cow was born which 

 used to pass finely-sifted nourishment through the 

 bladder. They cut its anus open, but it quickly grew 

 together again, and they did not succeed in keeping 

 it apart. 



We have now discussed the production of few off- 

 spring and many, the nature of supernumerary or 

 deficient parts, and also monstrosities. 



In some animals superfetation " does not occur at V 

 all, in others it does ; and among the latter some are f^^^' 

 able to complete the nourishing of the fetations, others 

 can sometimes do it and sometimes not. The reason 

 why in some animals superfetation does not occur is 

 that they produce one offspring only. Thus, it does 

 not occur in solid-hoofed animals and in larger animals 

 than these, because on account of their size the 

 residue goes to the fetation and gets used up. All of 

 these have large bodies, and large animals have large 

 embryos, proportionate to their size ; that is why the 

 embryo of an elephant is as big as a calf. Superfeta- 

 tion, however, does occur in animals which produce 

 numerous offspring at a birth, because where there 

 are more than a single offspring one is really a super- 

 fetation upon another. Of these animals, those that 

 are large, such as man, complete the nourishing of the 

 second fetation, if the second copulation has taken 

 place not long after the first ; such an occurrence 

 has in fact been observed. The reason is as already 

 stated : Even in a single act of intercourse the semen 



pregnancy. The young resulting from the second coitus are 

 usually born at the same time as those resulting from the 

 first coitus, but are smaller. See F. H. A. Marshall, Physi- 

 ology of Reproduction* (1922), 154. 



447 



