TEGUMENTARY ORGANS 391 



larger Crustacea {inde infra), and I should have placed it with them, 

 except for the very distinct statement of Mr. Newport with regard to 

 the development of the integument in Meloe. According to Mr. 

 Newport's researches, the integument of the young Meloe is at first 

 composed of polygonal nucleated cells, the largest of which is about 

 axrffrr of an inch in diameter. As the animal grows, the nuclei divide 

 and subdivide by a process of fission, and the integument becomes 

 composed of several layers. After awhile, the deeper of these undergo 

 a fibrous metamorphosis, and constitute a fibro-cellular structure, 

 which gives attachment internally to the muscles, while the 

 external layers continue to grow, and to be reproduced as distinct 

 cells. 



If this were the mode of development which obtained in all 

 Insecta we must consider their chitinous integument to be produced 

 by conversion of the previously existing cells of the ecderon. How- 

 ever, Leydig's statements are equally decided, that the integument of 

 Gorethra presents no appearance of cellular origin, and the question 

 may, therefore, for the present, probably be considered undecided. 



The calcified integument of the Crustacea presents the same 

 general structure as that of the other Annulosa, consisting of super- 

 posed chitinous, more or less fibrous lamellae, the outer of which are 

 infiltrated with a calcareous deposit. In the small transparent 

 Crustacea, as we have already seen, the integument is composed of 

 structureless layers , developed by excretion on the surface of the 

 ecderon, and even in the largest forms, the minute hairs, &c., present 

 precisely the same appearance ; but in the thick integument of the 

 Decapoda, certain layers of the shell have been described, not without 

 considerable show of reason, as possessing a cellular organisation 

 (Carpenter). ' • - 



I have carefully examined the shell of the common crab in relation 

 to this point, and the following- are the results of my investigation. 



It appeared to me in the first place, that, without seeking for a 

 moulting crab, the structure of the integument in its uncalcified state 

 might be readily ascertained by examining the soft membrane con- 

 necting the articulations of the limbs which, as is well known, is 

 continuous on either hand with the calcareous integument, and passes 

 into it. In a section of this soft layer {fig. 312. a), I found from 

 within, outward, i. The enderon («) composed of connective tissue, 

 excavated by vascular channels, and containing numerous aggregations 

 of pink and yellow pigment, frequently disposed in a stellate form, 

 or even forming anastomosing net-works along the rudimentary 

 elastic fibres of the tissue. 2. The surface of this {V) was constituted 



