DIRECT DEVELOPMENT. 211 



with design" — we have only to remember the fate of 

 the tapeworm's eggs — that by the larval state the 

 period of infancy and weakness is prolonged, and the 

 period of maturity and efficient care for the continuance 

 of the species delayed, it follows that curtailments and 

 reductions, consequent on adaptation have, as advan- 

 tageous modifications, a prospect of perpetuation. As 

 in Amphibians the prolongation of the larval phase may 

 be effected by natural circumstances and artificial ex- 

 periments, so in like manner a compression of the phases 

 of transformation, and a general curtailment of the 

 metamorphosis is imaginable. In the class of Amphi- 

 bians we have, in fact, several examples of curtailed and 

 modified metamorphosis which bridge over the apparent 

 chasm between development with and without transfor- 

 mation, and render direct development comprehensible 

 as being gradually acquired. Amphibians will endea- 

 vour to extend themselves wherever they are invited by a 

 sufficient supply of insects, and the black salamander of 

 the mountains (Salamandra atra) has even overcome the 

 impediment which might have been deemed insurmount- 

 able, the absence of water for its larvae. It does not lay 

 its eggs like its congeners, but only two are received 

 into the oviduct, and the fluids secreted from its walls 

 replace the marsh to them and to the larvae which 

 emerge from them. Here, and not when separated from 

 the parent, do the gills make their appearance, while the 

 other eggs, gradually following, are devoured by the 

 hungry larvae. The metamorphosis of the black sala- 

 mander, respecting which, unluckily, no recent investi- 

 gations have been made, thus takes place within the 

 parental body, and there is no difficulty in imagining 



