EMBRYOLOGY OF THE LOCUST. 277 



one plan througbout. The lining membrane is a layer of epithelial cells, 

 which are of various forms, characteristic for each division of the caual. 

 This layer may or taay not have an interior cuticula or thin homogene- 

 ous coat secreted by the cells. lu all the front part of the caual, the 

 cuticula is thick and resistant, and serves to form the hard ridges and 

 spines in the oesophagus, crop, and proven tricle. In the stomach, the 

 cuticula is very thin and delicate, and I thiuk, but am not sure, that it 

 is there pierced by numerous minute pores, through which pass fine cilia. 

 In the diverticula, the cuticula is somewhat more developed. On the 

 intestiual folds, it is armed with very numerous and very delicate spines. 



Outside of the layer of epithelial cells there comes first, at least in 

 some parts, a very thin basement membrane, next to which follows the 

 layer of connective tissue, and finally the muscles, which form a circular 

 and a longitudinal coat, both of which are unequally and variously de- 

 veloped in the different segments of the tract. 



The muscular and the connective layer are permeated by innumerable 

 fine air-tubes, or trachese. The trachese themselves present the same 

 histological p'eculiarities as those of other insects, and as I have described 

 in my article on the trachese of the water-beetle {HydropMlus) of Europe, 

 published in the Archives de Fhysiologie in January, 1876. Externally 

 there is a layer of flat epithelial cells, which secrete the spiral threads 

 and inner chitinous coats. 



My observations have also extended to other parts of the body, par- 

 ticularly to the genital system, and I shall be able in my final report to 

 communicate many new observations on these organs. It does not 

 seem to me, however, desirable to enter further into details at present, 

 as it would be difficult to give any satisfactory account without the aid 

 of figures. I have been able to trace some of the principal stages of 

 development of the eggs and spermatozoa, but must reserve the discus- 

 sion of them until later. 



EIVIBRTOLOGY OF THE ROCKY MOUNTAIN LOCUST. 



It was hoped that we should be able to give quite a full summary of 

 the principal changes in the life of the locust before leaving the egg, 

 but it has been found impracticable to do this. We therefore present 

 the following description of the egg, and of the embryo just before 

 hatching, taken, with some corrections and omissions, from Mr. Packard's 

 Eeport on the Eocky Mountain Locust.^^ 



The egg is curved, cylindrical, 0.21 inch (oj millimeters) in length, more 

 pointed at the posterior than the anterior end. The posterior end is 

 contracted just before the extreme tip, which is smooth, the more or less 

 regular pits in the crust which covers the chorion, or egg-shell, being 

 here obsolete. We have been unable to discover any micropyle, or pas- 

 sage for the spermatozoa. The posterior end points downward in the 

 egg-mass, so that the exit of the young locust from the anterior end is 



^Report on the Kocky Mountain Locust and other Insects, &.c , loe. cit. 



