THE DEVELOPMENT OF THE TADPOLE. 187 



means the case at first, as all muscle, even after possessing much 

 of the character of real muscle, is unstriped. Not till quite the 

 end of March could the division of the muscle bands of the back 

 and tail be found to be striped, these being the first to become 

 possessed of this character. All muscle at first is of this unstriped 

 nature, and does not become striped till it has become capable of 

 being used by the animal in the movement of the organs to 

 which they are attached. A peculiarity with respect to the tail 

 muscles is that before their degeneration they lose their striped 

 appearance, and the parts separate from each other, looking 

 almost like so many minute rods, which, having been at one time 

 in a bundle, have become separated from each other and broken 

 at their ends. The tendons whereby the muscles are attached to 

 the bones appear in early stages to be derived from the sarco- 

 lemma, or covering, which surrounds each fibre of a muscle. 

 This sarcolemma appears stretching from each individual muscle- 

 fibre, and coalescing together into a point is thus inserted into the 

 cartilage and attached to the bone. 



EXPLANATION OF PLATES XVII. AND XVIII. 



Figs. 1, 2, 6. — Early stages of brain and muscle. 



Fig. 3. — Vertical section of brain, showing the commencement of 

 separation into lobes. 



,, 4. — Horizontal section of brain of April 30th, showing cerebrum 

 with lateral lobes, mid-brain with optic lobes, and distribu- 

 tion of white and grey matter in striated lines, and medulla 

 oblongata, etc., with commencement of ten pairs of nerves, 

 bounded on either side by a chain of cartilage, showing 

 commencement of vertebrae. 



,, 5. — Vertical section of brain, with pineal gland. 



,, 7. — Vertical section, showing olfactory and optic nerves, with 

 position of auditory sacs. 



,, 8. — Vertical section of same, showing lamina terminalis and dis- 

 tribution of grey and white matter, with ventricles. 



,, 9. —Cartilage developing, with insertion of round cells developing 

 into a chain of muscle, 



,, 10. — Three bands of muscle fibre, in different stages. 



,, 11. — Muscle of the tail desquamating and being absorbed. 



,, 12. — Three muscle fibres, in different stages, showing separate 

 nuclei arranging themselves so as to form striped muscle. 



n.c, neural canal; m., muscle; m.p., muscle-plate; 6r. , 

 brain ;/.6., fore-brain; m.h., mid-brain; no., notochord ; 

 me., medulla oblongata; sp.c, spinal cord; m.c, mouth- 

 cavity ; au. , auditory sac ; c6. . cerebellum ; op. I. , optic 

 lobes; ol., olfactory lobes; ce. , cerebrum; v.c, vertebral 

 column ; Iv., lateral ventricle ; 3 v., 3rd ventricle ; 4 v., 4th 

 ventricle ; p.g., pineal gland ; ca., cartilage. 



