December 30, 1898.] 



SCIENCE. 



937 



that behind or above the arms, and these 

 two categories are the chief ones recognized 

 by Mr. Boulenger. The former mode is 

 exemplified by all the species of Discoglos- 

 sids and Pelobatids; the latter by the Bufo- 

 nids, Hylids and Ranids. Four kinds or 

 degrees of amplexation are represented by 

 admirable illustrations in Mr. Boulenger's 

 work and are here reproduced. Among 

 the Pelobatids the hands join on the pubic 



^^iT'- 





Amplexation of ' Eana arvalis.' 



region in Pelobates, while the forearms meet 

 on the pubic region in Pelodytes. It will be 

 in order now for some observer to tell us 

 how Scaphiopus practices amplexation ; the 

 various accounts hitherto published fail to 

 give the requisite information. 



Every sojoui-ner in the country must have 

 noticed masses of transparent jelly-like 

 spheres in the water, but none in the 

 United States could refer such masses with 

 certainty to the parent species. In Europe, 

 however, such an identification can be 

 made in almost every case, and Mr. Bou- 

 lenger gives a synopsis for that purpose, 

 and adds illustrations of the oviposition of 

 seven species representing all of the five 

 European families. Some of these illustra- 

 tions are here copied. 



The tadpoles of the European anurans 

 have also been described and figured, and 



each species may be readily identified by 

 means of an excellent analytical key (105- 

 109). The tadpoles of Rana, for example, 



Eggs of Pelodytes. 



are differentiated inter se by the relative 

 width of the interocular space, the series of 

 labial teeth, and the form of the tail. Mr. 

 Boulenger deduces the generalization that 

 " the structural differences which separate 

 the genera and species in their tadpole con- 

 dition reflect, on the whole, pretty accu- 



P^ 



^ f^ 



Eggs of Bufo. 



rately the system based upon the perfect 

 animals, although here and there the modi- 

 fications are of unequal importance. We 

 must bear in mind, however, that such a 

 correspondence, if existing in the European 

 Batrachians, is not universal. It is aptly 

 added : " Larval forms such as the tadpoles 

 are outside the cycle of recapitulation, the 

 ontogeny being broken by the intercalation 

 of the larval phasis." 



