940 



SCIENCE. 



[N. S. Vol. XII. No. 312. 



Pleistocene Macrauchenia ; the other an as- 

 tonishing imitation of the horses, an imita- 

 tion so detailed and so close that it has 

 misled Ameghino into believing that this is 

 the actual phylum of equine descent. The 

 resemblance is striking in all parts of the 

 structure ; in the teeth, the skull, the back- 

 bone, the limbs and especially the feet. The 

 less advanced forms have tridactyl feet, but 

 with the lateral digits already greatly re- 

 duced, while the more differentiated species 

 surpass the true horses in strict monodactyl- 

 ism, the splint-bones being almost sup- 

 pressed and represented only by minute 

 nodules of bone. Yet these wonderfully 

 horse-like creatures prove, on examination, 

 to be not even perissodactyls I A more re- 

 markable and instructive case of conver- 

 gent evolution it would be difiBcult to imag- 

 ine. 



The Astrapotheria were the largest of 

 Santa Cruz mammals. In them the great, 

 vaulted skull had such shortened nasal 

 bones as to suggest the presence of a pro- 

 boscis, and slender, edentulous premaxil- 

 laries. The canine teeth in both jaws are 

 enlarged to form powerful and formidable 

 tusks, the premolars are reduced in size and 

 number, while the molars are enlarged. 

 The grinding teeth display a remarkable 

 likeness in size and pattern to those of the 

 northern rhinoceros, Metamynodon, from the 

 White Eiver beds — another example of con- 

 vergent development. The Astrapotheria 

 would appear to have become extinct before 

 the Pleistocene, and it must be the object of 

 subsequent studies to determine whether 

 the group is really entitled to ordinal rank, 

 or whether it should be referred to the 

 Litopterna. 



I am not prepai-ed to express an opinion 

 as to the taxonomic position of Homalodon- 

 totherium, one of the most curious of the 

 many curious Santa Cruz hoofed-animals. 



The Primates are not very well known 

 as yet, for the fossils are seldom so com- 



plete as those which so often rejoice the 

 heart of the student who works with the 

 other groups. So far as they are under- 

 stood, the Santa Cruz monkeys would ap- 

 pear to be as characteristically South Amer- 

 ican, and as different from those of the 

 northern hemisphere, as we have seen to be 

 the case among the Rodentia. 



This exceedingly brief outline sketch 

 will have served its purpose if it makes 

 clear the wonderful character of the Santa 

 Cruz fauna and its radical differences from 

 the contemporary life of the northern hem- 

 isphere. Much remains to be done before 

 the full account of these splendid collections 

 can be published. I have attempted merely 

 to describe their general nature and the im- 

 pression which they make upon an observer 

 whose studies have hitherto dealt with 

 northern types. 



W. B. Scott. 



Peinokton Univeesity. 



la THERE ANY DISTINCTION BETWEEN 

 SEXUAL REPRODUCTION AND ASEXUAL 



REPRODUCTION r 

 The following pages contain rather a full 

 outline of the views advanced by Professor 

 Richard Hertwig in a recent lecture* in 

 which he discusses the relation between fer- 

 tilization and reproduction. I have en- 

 deavored to make this more in the nature 

 of an abridged and revised translation than 

 a review, for it seemed best to follow as 

 closely as possible Professor Hertwig's own 

 way of presenting the subject, which is as 

 follows : 



Everyone will admit that most of our 

 general conceptions in biology are greatly 

 influenced by our knowledge of the higher 

 animals and plants. This fact is made very 

 evident to all who study the reproduction 



* ' Mit welohen Recht untersoheidet man geschleot- 

 liche und ungesohlechtliche Fortpflanzung ?' Vortrag, 

 gehalten am 7, November, 1899. Aus den Sitzungs- 

 beriohten der Gesellschaft fiir Morphologie und Pbysi- 

 ologie in Muncben. 1899. Heft. II. 



