250 SOME RECENT 



raised as to the embryo being really a human one ; 

 and Professor His, one of the most expert of 

 embryologists, asserted roundly that Krause must 

 have made a mistake, and that his specimen was 

 a chick embryo and not a human one at all. An 

 ardent, almost furious, discussion arose, and con- 

 tinued for many years : it is indeed only within 

 the last twelve months that the points at issue have 

 been finally put at rest, and it has been shown 

 that while Krause was right in describing his 

 embryo as a human one, he was mistaken in regard 

 to the supposed peculiarity in the allantois, the 

 bladder-like vesicle which he took for the allantois 

 being merely a pathological dilatation of the allantoic 

 stalk. 



Among Invertebrates the resemblances between 

 the early larval forms of allied groups are equally 

 striking : the veliger and trochophore larvae, for 

 example, or the nauplius larva of Crustacea, having 

 not merely very wide zoological distribution, but 

 presenting marked constancy in essential, or even 

 in minor characters in the groups in which they 

 occur. 



That the early larval stages of a prawn, a cyclops, 

 and a barnacle ; or of a reptile, a chick, and a man, 

 should be so closely similar that it is possible to 

 mistake one for the other, is undoubtedly a very 

 remarkable thing; and it was perhaps inevitable 

 that there should be at first a tendency to over- 

 estimate the exactness of this resemblance. Em- 

 bryologists have indeed too often overrun their 

 facts; and, misled by the undoubtedly striking 



