34 ME. M. LA.TJEIE ON THE 



on its sides is well marked here, as ia Scorpions, tlie former 

 iDeing smaller and more closely packed. 



The central eyes are formed, as in Scorpions * and Spiders t, 

 by an in-pushing from in front of ■where the eye is about to be 

 formed, the dorsal wall of which in-pushing forms the retinal cells, 

 while the ventral wall forms a layer of flattened cells bounding 

 the retina on its ventral side. The nervous system being already 

 separated from the skin in my younger embryo, I cannot say 

 whether or not part of thecerebral ganglion is formed from theoptic 

 in-pushing as in Scorpions. As in other Arachnids, the central 

 eyes are diplostichous and the lateral eyes monostichous, the latter 

 being formed by a modification of the hypodermis-cells in situ. 



Coxal Gland. 

 The earlier stages of this structure are not represented in my 

 specimens. In the younger it is already a considerably coiled 

 tube. The tube is lined by cubical epithelium, the cells of which 

 have round lightly- granular nuclei. Towards the front end a 

 duct passes from the coiled tube and opens to the exterior on the 

 posterior face of the basal joint of the third appendage (PI. V. 

 fig. 23). The epithelium lining the duct differs from that of the 

 coiled tube, the nuclei being more closely packed, somewhat 

 larger, oval, and more darkly staining. They resemble pretty 

 closely the nuclei of the hypodermis, and as the duct has a thin 

 cuticular lining, it probably represents the ectodermal part of the 

 coxal gland. JN^o trace of an enlarged terminal sac, such as that 

 described by Faussek j in Fhalangium, could be found, but it 

 may be present in younger stages. 



The Respiratory Organs. 



The lung-books in the Pedipalpi are two in number, the first 

 lying under the large genital plate, and the second under the next 

 sclerite, which corresponds to the third free segment. An early 

 stage of development is shown in PI. V. fig. 22, which is a longi- 

 tudiual section to one side of the middle line. i. is the genital 

 plate, and iii. the sclerite immediately behind it. The two 

 resemble one another so closely that a description of one of them 

 will serve for both, iii., then, consisti? of a distinct outgrowth 



* Laurie, Q. J. M. S. vol. xxxi., and Parker, Eull. Mus. Comp. Zool. Harvard 

 vol. xiii. 



t Locj, Bull. Mus. Comp. Zool. Harvard, vol. xii. 



I Faussek, Travaux de la Soc. d. Nat. St. Petersb. vol. xxii. (Eussian) ; 

 Abstract in Biol. Oeutralbl. 1892. 



