Januabt 26, 1906.] 



SCIENCE. 



151 



physiological regeneration. It is a normal 

 part of the ontogeny of these specialized in- 

 sects, but it is an interpolated, a esnogenetic 

 condition. That is, although now a regularly 

 recurring phenomenon in the life of these in- 

 sects, it is distinguished only by the inevitable- 

 ness and regularity of its occurrence from any 

 occasional processes involving profound regen- 

 eration. It seems to me quite analogous with 

 such cases of regularly recurring physiological 

 regeneration as the moulting and new-growth 

 of the plumage of birds, the casting off and 

 new-building of the antlers of stags, the loss 

 of the peristome and the formation of a new 

 one in Stenior, etc.; in other words, with all 

 those cases mentioned by Morgan in illustra- 

 tion of his definition of physiological regen- 

 eration. 



In the two special cases of physiological re- 

 generation in insects here called attention to, 

 we may distinguish between regeneration of 

 the ventricular epithelium from tissue (cells) 

 of its same kind, and the regeneration of 

 wings, legs, mouth parts and antenna from 

 cells not belonging to similar organs but 

 simply forming part of the continuous larval 

 derm. In this latter case of regeneration, too, 

 the ' regenerated ' parts are in all cases differ- 

 ent from preexisting parts and in some cases 

 (wings', for example) are wholly new parts. 

 One might say that, this is not regeneration 

 at all, but simply development (ontogeny). 

 But in numerous cases of true restorative 

 regeneration the new parts do not agree exactly 

 with the replaced ones; often they are mark- 

 edly smaller, they lack segments, they lack 

 many details; they are cases of teratogenesis. 

 Por example, the cockroaches (Blattidse) have 

 the capacity of regenerating lost legs, or rather 

 parts of legs; but whereas the normal leg has 

 always five tarsal segments, the regenerated 

 one has always four. All, regeneration may, 

 of course, be looked on as a phenomenon of 

 ontogeny; a regulation. In practically all 

 animals which can regenerate at all, the ca- 

 pacity for regeneration is much greater in 

 immature life than in adult life: in many, 

 indeed, it exists only in the immature stages. 



In connection with this brief reference to 

 the occurrence of physiological regeneration 



in insects, it may not be amiss to refer, even 

 more briefly, to our present knowledge of 

 ordinary or what is called, for the sake of a 

 provisional distinction between the two cate- 

 gories, restorative or accidental regeneration 

 among insects. It has long been known that 

 certain insects of incomplete metamorphosis, 

 notably many Orthoptera, have the power of 

 regenerating lost parts of legs, antennse and 

 certain other externally produced organs, as 

 tracheal gills. Associated with this regen- 

 erative capacity occurs, in some insects, at 

 least, self-mutilation or autotomy. In addi- 

 tion, it has also long been known that if the 

 legs or antennae be cut off from the larva of 

 certain insects with complete metamorphosis 

 (moths, beetles and others) the adult will ap- 

 pear with ' regenerated ' legs or antennae, some- 

 times perfectly normal in size and form, some- 

 times normal in form but reduced in size, 

 and other times abnormal (usually lacking 

 distal parts) in form. But, as I have already 

 pointed out in a paper on the regeneration of 

 the larval legs of silkworms,^ this latter 

 kind of ' regeneration ' may not be restora- 

 tive regeneration at all, but a phenomenon 

 of physiological regeneration incident to the 

 regular process of development of the im- 

 aginal legs, antennae, etc., of insects of 

 complete metamorphosis in the course of 

 which the larval organs disintegrate and the 

 imaginal ones get formed from histoblasts 

 which lie in such position, at least in early 

 larval life, as to be uninjured by any cutting 

 of the larval legs. Finally, as I have shown 

 in the paper just referred to, the larvae of at 

 least one species of moth, Bomhyx mori, have 

 the capacity of regenerating during larval life 

 both thoracic (jointed) legs and abdominal 

 (prop) legs. Tornier^ also states that the 

 larvse of the meal worm, Tenehrio molitor, 

 can also regenerate, before pupation, cut off 

 legs, or parts of legs.* 



'Jour, of Exper: Zool., Vol. I., pp. 593-599, 

 1904. 



"Zool. Anseig., Vol. 24, 1901. 



' For accounts giving reviews and bibliography, 

 in some degree of completeness, of the recorded 

 cases of experiments and observations of regenera- 

 tion, in insects, see Brindley, ' On Certain Char- 



