2 Transactions of the Society. 



a subject upon M'liich there were practically only three existing 

 authorities. The first of these is Dujardin,* a keen-eyed observer, 

 •who saw a good deal, but unfortunately, as far as the Orihatidm 

 are concerned, drew conclusions from what he saw which have 

 formed a stumbling-block for most later writers. The second is 

 Nicolet, t and this may be treated as the only substantial work 

 upon the subject. The third is Claparede, $ whose work is 

 excellent as far as it goes, but it only deals with one very ex- 

 ceptional species of this family, and that with a view to the 

 development rather than the anatomy. 



\\ hen I first commenced, my idea was simply to verify Nicolet's 

 work before repeating his account in my own book ; and to 

 ascertain that it was correct, not only for the one or two species he 

 had described, but also for others. As I advanced, however, I 

 found so much variation in different forms, and so many points 

 upon which I was not able to coincide with Nicolet's descriptions, 

 that I was led to devote the greater part of my leisure during the 

 summer and autumn of 1882 to the investigation: it has been 



Plate II. 



Fig. 1. — Male reproJuctive system of Nothnis theleproctus. x 50. a, a, lobes 

 of the testis ; h h, tlat portion, possibly vesicula seminalis ; cc, vasa 

 deferentia ; d, ductus ejaculatorius, with penis, penial skeleton, 

 and sclerites, &c. 



„ 2. — Penis and penial skeleton and sclerites of same species, x 600. 

 a, penis. 



„ 3. — Penis of same species, side view, x 1500. 



„ 4. — ^exaen oi Damwus geniculatus. X 1800. 



„ 5. — Female reproductive system of Oribata lapidaria, taken when the 

 creature has just emerged from the nymplial stage. X 40. a, 

 ovary ; b b, oviducts ; c, vagina ; d, ovipositor ; e, genital plates ; 

 /, anal plates. 



„ 6. — Female reproductive system of Cepheus tegeocranus, mature, showing 

 the oviducts full of eggs. X 60. Same lettering. 



„ 7. — Female reproductive system of Damceus geniculatus, mature, ovary 

 nearly exhausted, x 50. Same lettering ; and g, globular ex- 

 pansion of oviduct ; h h, copulative suckers (so called) ; i i, tendons 

 to genital jdates; jj, muscles attached to same tendons. 



„ 8. — Portion of the ovary and portion of oviduct of same species, up to 

 and including the globular expansion, x 120. Same lettering. 



„ 9. — End of trachea in acetabulum of leg of Leiosoma p dmicinctum. 

 X 180. a, edge of acetabulum ; h, coxa; c, trachea ; d, muscles 

 of leg. 



„ 10. — Kn&\. sSiC oi Nothrus theleproctus. x 100. a a, sac; 6 6, genital plates ; 

 c c, anal plates. 



* " Premier Me'moire sur les Acariens," Ann. des Sci. Nat., 3rd ser. iii. p. 5. 

 Journal de I'lnstitut, 1842, p. 316. 



t " Histoire Naturelle des Acariens, qui se trouvent aux Environs de Paris," 

 Archives du Museum, vii. (1855). Paris. 



\ " Studien an Acariden,' Zeitschr. f. Wiss. Zool., xviii. (1868) p. 446. 



