22 Transactions of the Society. 



considerable in the general form of the organ, and to a lesser extent 

 in the minuter structure ; if the double lines be tubules they would 

 be analogous to those in the nephridia.* The sac above described 

 (super-coxal gland) would correspond with the gland in the neph- 

 ridium, and the globular body with the vesicle. 



The position would seem to correspond fairly with that of the 

 green gland and the coxal glands, in the former of which Will 

 and Gorup-Besanez say that they found guanin,t and Huxley says 

 that if this be so there can be little doubt that it represents the 

 kidney, and its secretions the urinary fluid ;± while Eay Lankester 

 is inclined to look on the latter as homologous with the nephridia.§ 



I cannot say that I have succeeded in finding any actual 

 opening of the super-coxal gland to the exterior, but the extremely 

 small size of the creatures and of the gland, and the position of the 

 latter, make it very difiicult, and indeed Professor Lankester does 

 not seem as yet to have been more successful in this particular 

 respect with the larger forms which he has been dealing with. 



In HopJo'jjliora magna, about in a similar place to the above- 

 named super-coxal glands (as far as the peculiar form of Hophphora 

 will allow), I find, on each side of the body, a pyriform sac, having 

 the smaller end toward the legs, and the larger, blind end, toward 

 the centre of the body ; this sac has walls less finely granular than 

 the glands in Leiosoma, &c., but very glandular; I have not found 

 in it either the refractive points or the zigzag markings ; it is not 

 bent nor doubled on itself nor twisted ; there is a* globular vesicle, 

 darker in colour than the sac, on each side of it. These organs 

 require further investigation, but it would appear probable that 

 they are the homologues of the super-coxal gland and vesicle, 

 although presenting considerable difi'erences. 



TJie Exo-sJieleton. 



The only two points relative to the exo-skeleton which I intend 

 to refer to are: — 1. The tectum; 2. The mandible of the species 

 which Nicolet calls Leiosoma microcepliala. 



The tectum is a part which owes its name to Nicolet ; he alone 

 has pointed out the existence of such an organ ; as far as I know 

 it does not exist in any other creatures, and it will be seen from 

 the following remarks, that, in my opinion, it does not exist at all. 



iS'icolet's statement, when treating of the cephalothorax, is as 

 follows : — " In a large number of individuals, forming the first 

 division of the Oribatidx, the upper part of the cephalothorax is 



* See A. G. Bourne, " On the structure of the Nephridia of the Medicinal 

 Leech," Quart. Journ. jNIicr. Sol., 1880, pp. 283-302. 



t Gelehrte Anzeigen d. K. Baierischen Akad., No. 233, 1848. 



J 'The Crayfish,' 1880, p. 83. 



§ Proc. Roy. Soc, xxxiv, (1882) pp. 95-101. 



