130 rEOFESSOR E. EAY LANKESTEE. 



In previous publications ^ I have given some account of the 

 remarkable internal skeleton or entosternite of Limulus and 

 Scorpio. I have also drawn attention to the coxal glands of 

 the Arachnida, previously unknown^ and pointed out their 

 agreement with the ''brick-red glands^' of Limulus.^ Hitherto 

 I have not published any account of the microscopic structure 

 of the entosternite, nor any sufficient explanation of the micro- 

 scopic structure of the coxal glands. I propose to supply these 

 requirements in the present memoir, and, inasmuch as tlie 

 entosternites of Limulus and the other Arachnida are histolo- 

 gically a variety of the connective tissue, or vaso-fibrous tissue, 

 it will be convenient to include here a description of the more 

 important varieties of tissue belonging to the skeleto-trophic^ 

 group, which present themselves to our notice in Limulus and 

 its allies. 



It will be found that there are remarkable points of agree- 

 ment between Limulus and Scorpio in respect of some of these 

 tissues. On the other hand, the observations have value on 

 account of the necessity which exists for a detailed and com- 

 prehensive study of the connective tissues and other tissues of 

 the skeleto-trophic group in both Arthropoda and Mollusca, 

 before we can pretend to offer any satisfactory account of the 

 vascular system in those groups, and of the " lacunar " connec- 

 tion between arteries and veins, which is confidently described 

 and discussed by all zoologists, but has never yet been demon- 

 strated to exist, in a manner satisfying the requirements of 

 modern histology. 



With regard to the anatomical connections of the entoster- 

 nites in Limulus and Scorpio, and especially with regard to the 

 complicated series of muscles which are attached to these struc- 

 tures in each of those animals, I would refer the reader to a 

 memoir now in course of publication by the Zoological Society 



' "Limulus an Arachnid," this Journal, ISSl. 



2 "The Coxal Glands of Scorpio," ' Proc. Rcyal Soc. London,' No. 221, 

 1882. 



' I regard the skeletal, vascular, and hsemoljmph derivatives of the meso- 

 blast (including Mecznikow's " phagocytes ") as forming a natural group of 

 tissues to which the name " skeleto-trophic," is appropriate. 



