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XIX. The Natural History, Anatomy, and Development 0/ Meloe (continued). 

 By George Newport, Esq., F.B.S., F.L.S. 8fc. 8fC. 



Third Memoir. 



The External Anatomy of the Larva of Meloe' in its Relation to the Laws of Development. 



Read November 2nd, 1847. 



HAVING traced the natural history of Meloe, in the preceding Memoirs 5 I shall now 

 examine its anatomy, with reference to those principles which regulate the formation of 

 animal bodies, and which seem to be the links of connexion which associate peculiarities 

 of instinct with the evolution, and with the functions of special structures, — commencing 

 this with the Anatomy op the tegument. 



1. The Tegument of the young Larva. 



The tegument, the parietal tissue of the body, little important as it may seem to be 

 when cursorily examined in the adult Vertebrata, is nevertheless, in a physiological point 

 of view, both in the vertebrated and in the invertebrated animal, the primary and essential 

 foundation-structure of the organized being. Like the earlier tissues of plants, it is at first 

 composed entirely of nucleated cells. It is derived immediately from a delicate, transparent 

 layer of semifluid cells which constitute the blastodermic envelope that is formed around 

 one portion of the yelk shortly after the disappearance of the embryo vesicle in the ovum, 

 subsequent to impregnation. This has already been shown in the brief outline of the course 

 of development, and in the delineations which I have given of the ovum of that " atomie" 

 of creation, Sty lops* ; and I shall hereafter have to show that the same general laws which 

 govern the development of that atomic existence regulate equally that of Meloe and of 

 Man. This blastodermic layer of cells, folded on itself, and partially inclosing the yelk, is 

 the structure from which the whole of the organized parts of the body concerned in the 

 voluntary functions of the animal, are immediately derived ; and, as embryologists are 

 aware, it is to the foldings, the intus-susceptions, the extension or the shortening of 

 portions of this structure that the primary form of the animal body is entirely due ; 

 whether it be that of the uniform and simply articulated worm, or of the rudimentary 

 embryo of the most perfect of organized beings, Man. 



The principles which thus regulate the ultimate form of the embryo that is to be, and 

 the origination of its future limbs, ere it has any definite structural existence, regulate 

 also the whole of its growth and metamorphoses, whether these are gradual, uniform, and 

 uninterruptedly continuous to their end, as in most of the Vertebrata, or whether they 

 are marked by more rapid and extensive evolutions at some periods than at others, as in 



* Linnean Transactions, vol. xx. p. 337. t. 14. f. 23-32. 



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