General Account of the Ithacan Anura. 9 



ABNORMAL EMBRACES. 



Some of our Anura have embraced forms not of the same order or 

 class. Occasionally, when placed in the same aquarium with a totally 

 different sort of animal, they may seize it. Such records are : 



Hyla pickeringii X Ambystoma punctatum. 



Chorophilus triseriatus X Ambystoma jeffersonianum. 



Rana sylvatica X Ambystoma punctatum. 



Rana pipiens X Amiatus calva. 



DEPARTURES FROM THE CUSTOMARY EMBRACE AND THEIR 



SIGNIFICANCE. 



Dr. Gill observes: 



The "amplexation" or mode of approach of the males on the females, is 

 characteristic, and in main features is common to the members of a genus, 

 so far at least as the European species are concerned. So generally in con- 

 formity with structural features has it been regarded that the principal 

 modifications have been used to differentiate and diagnose certain groups. 

 * * * Mr. Boulenger well remarks: "How exaggerated the importance 

 attached to this correlation, which, besides, holds good only for the European 

 forms, is now apparent to all." Nevertheless, within certain limits, the species 

 of a genus agree in their mode of amplexation; only a too strict taxonomy can 

 not be applied. For example, Mr. Heron Royer (Bull. Soc. Zool. France, 1890, 

 p. 205) recognized 7 categories of amplexation pectoral, axillary, supra-axillary, 

 inguinal, axillo-inguinal, lumbo-pubic, and lumbar. * * In fact, such 

 differences may be simple expressions of the relative size of the male and 

 female and must vary as do the sexes. But there is a sharp contrast between 

 amplexation round the waist and that behind or above the arms, and these 

 two categories are the chief ones recognized by Mr. Boulenger. 



I have seen the amplexation of the eight species under consideration, 

 and feel with Dr. Gill that " differences may be simple expressions of 

 the relative size of the male and female." In the eight species with 

 normally three types (pectoral, axillary, and supra-axillary) of embrace, 

 we have observed all the seven categories of Heron Royer but one 

 (lumbo-pubic). Furthermore, we can hardly consider that there is a 

 sharp differentiation between amplexation about the waist and that 

 behind or above the arms. In addition to size, the beginning of sexual 

 impulse, its height, its waning, or exhaustion after one mating, may 

 bring departures from the normal mode of approach. 



There are many chances for wrong conclusions regarding the tax- 

 onomic value of form of embrace, if based on few observations. At the 

 beginning of pairing, often the male grasps a leg or some part and locks 

 both arms together, keeping to the temporary hold until the normal 

 embrace can be permanently secured. Occasionally, when not at the 

 height of sexual impulse, or at the beginning of the breeding season, an 

 embrace may be recorded not of the usual type for the species in ques- 

 tion, e. g., the first record of the embrace of Rana clamata was more 

 of the Hyla type (Plate iv, Fig. 6) ; ever after, with one exception, how- 



