ORIGIN OF THE ANIMATED TRIBES. 



115 



We turn to the minutiae of organic structure and embryo- 

 logy, as affording us some further illustrations of an instructive 

 kind. It is now ascertained by microscopic research, that the 

 basis of all vegetable and animal substances consists of 

 nucleated cells ; that is, cells having granules within them. 

 Nutriment is converted into these before being assimilated by 

 the system. The tissues are formed from them. The ovum 

 destined to become a new creature, is originally only a cell 

 with a contained granule. We see it acting this reproductive 

 part in the simplest manner in the cryptogamic plants. " The 

 parent cell, arrived at maturity by the exercise of its organic 

 functions, bursts, and liberates its contained granules. These, 

 at once thrown upon their own resources, and entirely depen- 

 dent for their nutrition on the surrounding elements, develop 

 themselves into new cells, which repeat the life of their 

 original. Amongst the higher tribes of the cryptogamia, the 

 reproductive cell does not burst, but the first cells of the new 

 structure are developed within it, and these gradually extend, 

 by a similar process of multiplication, into that primary leaf- 

 like expansion which is the first-formed structure in all 

 plants." Here the little cell becomes directly a plant, the full 

 formed living being. It is also worthy of remark that, in the 

 sponges, (an animal form,) a gemmule detached from the body 

 of the parent, and trusting for sustentation only to the fluid 

 into which it has been cast, becomes, without further process, 

 the new creature. Further, it has been recently discovered by 

 means of the microscope, that there is, as far as can be judged, 

 a perfect resemblance between the ovum of the mammal tribes, 



FIG. 72. 



B 



A, Early stage of Mammalian Ovum ; B, Young of Volvox Globator. 



during that early stage when it is passing through the oviduct, 

 and the young of the infusory animalcules. One of the most 



1 Carpenter's Report on the Results obtained by the Microscope in 

 the Study of Anatomy and Physiology, 1843. 



i2 



