2 NATURAL SCIENCE. July. 



January, 1896), Mr. T. D. A. Cockerell explains his reasons for adopt- 

 ing such a method in teaching entomology to the students of the New 

 Mexico Agricultural College. So far as we can find out, systematic 

 work, as such, is not a part of the biological course in any of the well- 

 known British morphological laboratories. It certainly has no place 

 in the courses prescribed for beginners, or for medical students, and 

 although in these days, when the study of variation is receiving great 

 attention, senior students can hardly avoid some species-work, still the 

 species-work comes as an accidental appanage of the study of individual 

 variations. While we are fully willing to admit with Mr. Cockerell 

 that in the hands of a competent teacher species-work might become 

 a valuable mechanism for education, we are not prepared to agree 

 that it should be a substitute for a more general course. Still, to 

 many minds the exact study of the concrete specific differences among 

 a. limited set of organisms would give a certain definiteness, and what 

 would be appreciated as practicalness, to the study of biology. We 

 should welcome the addition to an elementary course of the study of 

 a prescribed set of species. A genus of reptiles, or bees, or butterflies, 

 might be taken that included a limited number of species, and the 

 characters of the species should be taught dogmatically and learned 

 upon the specimens, just as the elementary student of anatomy learns 

 the characters of human bones. 



On the other hand, in the case of the advanced student, a larger 

 and more scientific study of species should be as natural a part of his 

 training as the study of embryology, or of dentition. Along with this 

 the methods of proper description, the rules of nomenclature, and the 

 chief difficulties in the way of identifying species, should be studied. 

 The relation of individual variation to varieties and to species in a 

 definite group should certainly be included. Morphology and the 

 study of species cannot be divorced. At some period of his career 

 the most abandoned morphologist, or the most devoted systematist, 

 cannot avoid passing over into the problems of the other branch of 

 biology, and this should be recognised in his training. 



Habits as Diagnostic of Species. 



Prior to Mr. Cockerell's study of Perdita, a genus of bees, seven- 

 teen North American species were known, two of which were not 

 ■considered valid ; he now recognises seventy species : twenty-six in 

 both sexes, twenty-six only in the male, eighteen only in the female ; 

 twenty-three being from single specimens. Without examination of 

 the material it may be presumptuous to criticise, but it must be 

 confessed that in the absence of knowledge of nesting habits, 

 insufficient evidence as to double broods, and silence as to the effects of 

 parasites on structure, this wholesale coining of new species appears 

 rash and likely to lead to confusion hereafter. It must, however, be 

 admitted that Mr. Cockerell has done good service in calling attention 



