Notes on Mr. Cross's Acarus. 61 



Acarus horrldus, by the mere aid of the materials which he 

 points out. These means, even supposing them to have been, 

 under the circumstances, indispensible to the appearance of the 

 animal, have acted but as simple stimulants, which, like those 

 exciting organic germination in a grain of corn, have hasten- 

 ed the developement of eggs, similar to that contained in the 

 female individual sent by Mr. Cross himself, — eggs which 

 happened to be laid or deposited upon the surface of the lava 

 made the subject of experiment. 



Being unacquainted with the works written by Mr. Cross, 

 upon the artificial and voluntary production of his Acarus, 

 we are ignorant whether the animal comes fresh from the 

 experiment in its perfect state, or if, as would be more con- 

 sonant with the laws which regulate the developement of or- 

 ganized beings, it passes through the different stages and 

 metamorphoses which are so familiar to us, in all the other 

 species of this genus; whether, in the experiments, it commen- 

 ces by being only a point, then a globule, then an egg, next 

 a young Acarus, having only six legs, and finally, a perfect 

 Acarus, with eight legs, male, or female without eggs, or con- 

 taining eggs, like that manufactured by Mr. Cross, a figure of 

 which, taken with the aid of the microscope, we have had 

 the honour of submitting to the Academy. 



But in viewing the production of Mr. Cross's Acarus in 

 this light, there still remains one great difficulty, — that of 

 knowing how and where these animals, naturally so vora- 

 cious, could find the nourishment necessary for their deve- 

 lopement ; since organized beings can increase in weight and 

 size, only by taking in the nutritive matter found around them, 

 and assimilating it by means of a mysterious power peculiar 

 to themselves. 



Physiology, in the present day, being more enlightened, 

 and consequently but little credulous in the matter of spon- 

 taneous organizations, and above all of organizations formed 

 by the hand and at the will of man ; convinced, moreover, by 

 observation, that all organized beings result, by tissular exten- 

 sion, from a parent similar to themselves, and which alone 

 has received from nature the power of reproduction ; — this 

 physiology, exacting but little, does not demand from phy- 

 sics and synthetical chemistry, unaided by the living labora- 

 tories of which we have just spoken, the construction of an 

 Acarus, which is an animal almost as complicated as one of 

 the Mammifera, — but only that of a single muscous globule 

 ofProtosphteria, endowed, let it be understood, with the pro- 

 perties or attributes of organic life, viz. absorption, assimila- 

 tion, and the reproduction of its species. 



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