876 



SCIENCE 



[N. S. Vol. XXVI. No. 677 



should have more attention than it seems to 

 get. The whole matter of metamorphosis in 

 insects has been looked at too much from the 

 angle of the systematists, who have found " in- 

 complete " and " complete " metamorphosis a 

 convenient taxonomic character, and of the 

 nature study teachers, who have found it a 

 subject of fascinating interest to children. 

 The true biologic significance of the process 

 has been pretty consistently overlooked. 

 Montgomery does well to recall attention to it 

 and to suggest an interpretation of it of great 

 interest. 



However, before accepting this interpreta- 

 tion, or any other, or following it too far, we 

 should be sure we know the actual state of 

 affairs represented to us by the phrase " com- 

 plete metamorphosis." This commonly sug- 

 gests, first, the externally obvious, apparently 

 violent and radical changes from larva to 

 pupa to adult, and, second, the interesting in- 

 ternal phenomena of the histolysis of the 

 larval parts and histogenesis of the imaginal 

 parts. But we are very likely to let a tjrpe 

 or example of this total performance represent 

 to us the whole range of the phenomenon, 

 which is misleading. For as a matter of fact 

 every gradation can be found among insects 

 from the simple going over, with little or con- 

 siderable transformation, of larval parts into 

 adult parts, as taken to be characteristic of 

 " incomplete " metamorphosis, to the radical 

 disintegration and disappearance of the larval 

 parts with the fundamental new building of 

 the imaginal parts from isolated histoblasts, 

 taken to be characteristic of and common to 

 all insects of " complete " metamorphosis. 



During the last few years, various students 

 in my laboratory (particularly Mr. Powell) 

 and I myself have given some special atten- 

 tion to, the phenomena of insect meta- 

 morphosis, and have been able to break down 

 any inherited belief of ours (or belief acquired 

 from tradition and text-books) of the discon- 

 tinuity of " incomplete " and " complete " 

 metamorphosis. We have found insects of in- 

 complete metamorphosis (Hemiptera) show- 

 ing some of the characteristic phenomena of 

 complete metamorphosis and insects of com- 

 plete metamorphosis (Coleoptera) showing 



characteristics of incomplete metamorphosis. 

 And these not as individual variant or aber- 

 rant cases, but as conditions characteristic of 

 the development of species. 



That is, if the insects with more specialized 

 complete metamorphosis, as flies, ants, etc., are 

 to be looked on as metagenetic in character 

 {i. e., " with a life cycle consisting of two or 

 more individuals with alternation of sexual 

 and asexual reproduction"), and the insects 

 with most generalized incomplete metamor- 

 phosis as having a continuous (non-meta- 

 genetic) life cycle, the question arises as to 

 where, in the insect class, the difference first 

 appears. And if the whole process of meta- 

 morphosis differs in its most specialized and 

 its most generalized states only in degree ; if a 

 complete series of intergrading or connecting 

 states exists (as really does) ; where is the op- 

 portunity to interpret this process in the case 

 of certain insects as true metagenesis, and in 

 the case of others as a true continuous non- 

 metagenetic life cycle? 



Vernon L. Kellogg 



Stanfoed Uni-^'eesitt, Cal. 



BOTANICAL TEXT-BOOKS 



It is a pretty dull week when some one does 

 not put out a new botanical text-book intended 

 for high-schools, colleges and universities, and 

 not infrequently these consist of 300 to 600 

 pages each, covering a wide range of topics. 

 The great diversity of training given in the 

 colleges of our country and of Europe, makes 

 it next to impossible for any capable man to 

 produce a book all sections of which will fit 

 a large number of teachers. I think we may 

 well learn a lesson regarding this multiplicity 

 of books from the teaching of English lit- 

 erature. 



Instead of compelling each member of a 

 class to purchase complete sets of Burke, Pat- 

 rick Heni-y, Webster or Clay, select speeches 

 of these men are printed separately, which are 

 inspiring and can be used by the students ac- 

 cording to their different tastes. So here i» 

 botany, why should not some one, by this plan, 

 prepare a considerable number of pamphlets, 

 each suited to the needs of some teacher, 

 which his own judgment will lead him ta 



