THE HORSE. 



131 



developed; and they have not, therefore, 

 the attribute of a separate individuality. 

 Various phenomena hereafter to be detailed, 

 however, respecting the ' gemmiparous ' 

 production of living beings, when taken in 

 connection with that just cited, seem to ren- 

 der it by no means impossible that the in- 

 dividualization may be more complete in 

 other cases, so that independent beings of a 

 lower type may possibly originate in a per- 

 verted condition of the formative operations 

 in the higher. But no satisfactory evidence 

 has ever been aftbrded by experience, that 

 such ' equivocal generation ' has actually 

 taken place ; and its possibility is here 

 alluded to only as a contingency which it is 

 right to keep in view. That no higher type 

 has ever originated through an advance in 

 developmental power, may be safely as- 

 serted ; for, although various instances have 

 been brought forward to justify the asser- 

 tion that such is possible, yet these instances 

 entirely fail to establish the analogy that is 

 sought to be drawn from them.* 



* Thus, the author of the " Vestiges of the Natural 

 History of Creation " refers to the various modifications 

 which have taken place in our cultivated Plants and 

 Domesticated Animals, in proof that such elevation is 

 possible ; quite overlooking the fact that these external in- 

 fluences merely modify the development, without elevating 

 it, and that these races, if left to themselves, speedily revert 

 to their common specific type. And he adduces the 

 phenomena of metamorphosis — the transformation of 

 the worm-like larva into an insect, and of a fish-like 

 tadpole into a frog — as giving some analogical sanction 

 to the same doctrine ; totally overlooking the fact, that 

 these transformations are only part of the ordinary develop- 

 mental process, by which the complete form of the species 

 is evolved, instead of being transitions from the perfected 

 type of one class to the perfected type of one above it. 

 So, again, he quotes the transformation of the worker- 

 grub of the hive-bee into the fertile queen, as an example 

 of a similar advance ; without regarding the circumstance 

 that the worker is pltysicaUy higher (according to human 

 ideas, at least) than the queen, whose Instincts appear 

 limited to the performance of her sexual functions ; and 

 that the utmost which the fact is capable of proving, is, 

 that the same germ may be developed into two different 

 forms, according to the circumstances of its early growth. 

 It must always be borne in mind that the character of a 

 species, to be complete, should include all its forms, per- 

 fect and imperfect, modified and unmodified ; since in this 

 mode alone can that " capacity for variation " be deter- 

 mined, which is so remarkal)le a feature in many cases, 

 and is that which specially distinguishes the races of plants 

 and animals that have been subjected to human influence. 



" The development power which each germ 

 possesses, under the conditions just now 

 detailed, is manifested, not merely in the 

 first evolution of the germ into its com- 

 plete specific type, but also in the main- 

 tenance of its perfect form, and, within 

 certain limits, by the reproduction of parts 

 that have been destroyed by injury or dis- 

 ease. This reproduction, as Mr. Paget has 

 pointed out,* differs from the ordinary pro- 

 cess of nutrition in this, — that ' in grave 

 injuries and diseases, the parts that might 

 serve as models for the new materials to be 

 assimilated to, or as tissue-germs to develop 

 new structures, are lost or spoiled ; and yet 

 the effects of injury and disease are re- 

 covered from, and the right specific form 

 and composition are retained ; ' — and, 

 again, ' that the reproduced parts are 

 formed, not according to any present model, 

 but according to the appropriate specific 

 form, and often with a more strikingly evi- 

 dent design towards that form, as an end 

 or purpose, than we can discern in the nat- 

 ural construction of the body.' In the re- 

 production of the leg of a full-grown 

 Salamander after amputation, which was 

 observed to take place by Spallanzani, it is 

 clear that, whilst the process was from the 

 first of a nature essentially similar to that 

 by which its original development took 

 place, it tended to produce, not the leg of 

 a larva, but that of an adult animal. Hence 

 it is obvious that, through the whole of life, 

 the formative processes are so directed as to 

 maintain the perfection of the organism, 

 by keeping it up, so far as possible, to the 

 model or archetype that is proper to the 

 epoch of its life which it has attained. 

 The amount of this regenerating power, 

 however, varies greatly in different classes 

 of organized beings, and at different stages 

 of the existence of the same being ; and, as 

 Mr. Paget has pointed out,t it seems to 



In no instance has tliis variation tended to confuse the 

 limits of well-ascertained species ; it has merely increased 

 our acquaintance with the number of diversified forms into 

 which the same germ may devclope itself. 



* " Lectures on Reproduction and Eepair." 



t Loc cit. 



