120 DESCRIPTION OF THE PLATES. 



now become very strong, covers the young germ, 

 thus acting as a means of defence from external 

 injury. 



PLATE VI. Fig. 3, 4, 5, Are the same parts in progressive states of 

 developement. Fig 5. presents a bifurcated cha- 

 racter, probably from some accidental cause it 

 thus appears smaller than it is in the normal 

 state. 



Fig. 6. Represents the raw surface of the leg, already al- 

 luded to, in Car emus Mcenas, some time after 

 separation. A nucleated cell is seen in the 

 centre. This drawing was made from a very 

 small specimen, and was only procured in the 

 stage represented after great difficulty. 

 Fig. 7. Represents a longitudinal section of a very young 

 germ, for the purpose of showing its mode of 

 developement. The fibrous looking band which 

 surrounds it externally, is a circular canal 

 which belongs to a system of vessels described 

 in the text. The four striated bodies which 

 lie next to this canal are the rudiments of 

 the four joints of the future limb. The striated 

 appearance arises from the muscles already so 

 far developed, and the albuminous matter 

 within, and which they enclose, appears to 

 be pabulum for their farther nourishment. The 

 more defined globules, which may be observed 

 floating amongst the albumen, are oil glo- 

 bules. In the developement of this leg, it 

 will be observed that the external segments, 

 or those which are analogous to the thigh 

 and first tibial joints, are largest, and most fully 

 formed, a fact we would be led to expect, from 

 the circumstance of their formative cells being 

 the first thrown off from the original parent 

 nucleus, and consequently the first that would 

 take on a central or more independant action. 

 From a similar mode of developement, we see 

 that the second tibial and tarsal joints are the 

 smallest, as they are the last formed of the 



