14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



should not be bunched merely because it is difficult to distinguish 

 them. If it is possible to separate them, they should be separated. 



The conviction is constantly growing among biologists that we 

 really do not comprehend species. Multitudes of insect forms have 

 been confused under one specific name since systematic entomology 

 began. The scientific concept of the invertebrate species is grad- 

 ually growing less vague and more restricted. There is practically 

 no doubt that in most groups of insects, the Coccidse excepted, there 

 are many times more forms that will eventually be termed "species" 

 than have heretofore been recognized. Every year new results ob- 

 tained from a study of the early stages of insects force this convic- 

 tion upon us. (The Coccidas probably form an exception. Mr. J. 

 G. Sanders is authority for the statement that the species have been 

 largely split on characters pertaining to different ages of the same 

 stage.) Without doubt, bunching is infinitely more harmful to a 

 system of classification than splitting. Splitting, even if inju- 

 diciously done, does not give rise to actual error, but bunching pro- 

 duces all kinds of error in the bionomic literature, which errors, 

 moreover, are irremediable except through a restudy of the speci- 

 mens originally referred to. It goes without saying, however, that 

 forms can be properly separated only on constant structural charac- 

 ters pertaining to the same age or stage of development, and on 

 color, form, and size only when such are known to be constant. A 

 plea is herewith entered for judicious splitting, 1 up to the limit of 

 practicability. A reasonable degree of conciseness in the designation 

 of forms of insects is absolutely unattainable by any other means. 



A word is not out of place here bearing upon the causes of varia- 

 tion which give rise to vast multitudes of forms during the period 

 of greatest prolificacy of a group in any order of life. 



Mr. W. L. Tower, in his paper on Leptinotarsa (Carnegie Institu- 

 tion of Washington. Publication No. 48), has demonstrated that 

 variation is not inherent in the germ plasm, but is invariably induced 

 by external stimuli acting thereon. The demonstration consisted of 

 several experiments in which the stimuli were directly applied to 

 pregnant females of Leptinotarsa, so as to reach the germ plasm 

 within the contained ova. This one point is by far the most im- 

 portant contribution to science that the author makes in the whole of 

 his long and highly instructive paper. All variations are directly 

 caused bv the action of external stimuli — such as heat, humiditv, 



1 This term is adopted in a serious sense because it is both apt and expres- 

 sive. Splitting can be accomplished only along lines of fi rmation or natural 

 cleavage, and this is true of the proper division of taxonomic groups. 



