560 THE AMERICAN NATURALIST [Vol. XLII 



Alucitides. " The book, a large volume of 558 pages, is part of 

 Mr. Tutt's exhaustive "Natural History of the British Lepi- 

 doptera, ' ' this particular volume dealing with the plume moths. 

 The treatment of the several species is even more exhaustive 

 than that given by Mr. Scudder in his great work on the butter- 

 flies of New England; and as in Scudder 's work, the purely tax- 

 onomic details are relieved by chapters on general topics. 



In his two chapters, Mr. Tutt enumerates all the recorded 

 crosses between different species (hybrids) and between different 

 forms of the same species (mongrels), and gives numerous par- 

 ticulars about them. At the end of the book is an appendix 

 describing other cases made known while the volume was in press. 

 It appears that about 90 hybrid Lepidoptera are known, these- 

 being especially numerous among the Attacides and Anthro- 

 cerides. The well-established hybrids have been reared in cap- 

 tivity, and it is justly argued that many alleged hybrids found 

 at large must be regarded with extreme suspicion, as being quite 

 probably merely variations of one of the supposed parents. The 

 most distantly related species which have, when crossed, pro- 

 duced fertile eggs and subsequent larvae, are Saturnia pavonia X 

 GraeUsia isabellce; but in this case the larva could not be raised 

 to imagines. There is a very interesting discussion of the ques- 

 tion whether hybridization is capable of giving rise to new 

 species in a state of nature. This is considered extremely un- 

 likely, for the following reasons : 



"Even when hybridity is not difficult to procure between two 

 species, the progeny shows little fertility inter se, and, although 

 the males are more frequently fertile with females of either of 

 the parent species, the female hybrids are much more rarely 

 fertile with the males of the parent species, and at present few 

 hybrids show comparatively free fertility inter se. This appears 

 to be largely due to the anatomical and morphological upset in 

 the sexual organs of the female hybrids, an upset that frequently 

 finds its outward recognition in the development of gynandro- 

 morphic forms, in which the primary sexual characters are 

 often considerably modified, and correspondingly marked changes 

 take place in the secondary sexual characters. 



"Assuming, however, hybridity ever to take place in nature, 

 the hybrids themselves will often, presumably, follow one or 

 other of the parent forms so far as relates to its habits, time of 

 appearance, etc., and the chance of a male and female hvbrid„ 



