374 Mr. G. Newport on the Reciprocal Relation 



nervous force, as nervous force had ali-eady been shown by Fara- 

 day and Matteucci to develope electricity through the agency of 

 the organs of the electrical fishes. Thus the mutual convertibility 

 of these forces, the one into the other, in organic structure, ap- 

 pears now to be established, and the proof afforded of the cor- 

 rectness of the view or idea is due to Matteucci. Now what is 

 true of electricity in this respect may fairly be held to be correct 

 of the other forces, seeing that these have been correlated as phy- 

 sical influences, electricity with heat, heat with light, &c. 



It may be unnecessary, theretbre, to re-state now, in support of 

 the doctrine that the vital forces have a reciprocal relation with 

 the physical, those circumstances which have already been men- 

 tioned in the communications referred to. I shall merely add to 

 these a very few remarks, with facts derived chiefly from the In- 

 vertebrata, and which either arc new, or have not yet been ap- 

 plied to this inquiry, or have been directly observed by myself. 



It may be received as an admitted principle that it is necessary, 

 in addition to the previous communion of the sexes, and in order 

 to render continuous the changes then commenced, that the ovum 

 should either be maintained at the temperature in which it is 

 produced, or in one which is more or less increased, or in alter- 

 nations of degrees of heat; since, when the ovum is retained in 

 a medium of low temperature, the amount of which is more and 

 more diminished, the changes commenced are at first retarded, 

 then arrested, and with this arrestation vital force is propor- 

 tionately diminished instead of being increased. 



The amount of heat force derived from without, and required 

 for the evolution of life, varies, as we know, between wide ex- 

 tremes in different animals. Among insects there are some 

 Culicidce, even in this climate, which come forth during the depth 

 of winter and continuance of frost, if merely slight changes are 

 induced in the temperature of the air by solar rays. In the 

 colder region of Canada at that season there are other species 

 amongst the Perlidce which undergo their transformations, and 

 even pair, preparatory to depositing their ova, at similar low tem- 

 peratures. One species, Capnia vernalis, as I learn from my friend 

 Mr. Barnston, who has watched its habits, comes forth at the end 

 of winter, when the thick ice begins to crack, and changes from 

 the nymph to the perfect state in the crevices, leaving its slough 

 there, even when the temperature of the air has again sunk to 

 freezing. Another species of the same tribe, Brachyptera gla- 

 cialis, also makes its appearance at the same time, undergoes its 

 changes, and even pairs in the crevices of decaying ice*. As these 

 insects are short-lived in their perfect state, and as their larvae 



* See a paper by myself on " Pteronarcys regalis " in Trans. Linn. 

 Soc. vol. XX. pp. 451, 452. 



