366 ME. W. B. S. BENHAM ON THE TESTIS OF LIMULUS. 



" Limulus an Arachnid," viz., that the organization of Limiilus is closely similar to tka 

 of the Scorpions, and has no special agreement with that of any Crustacea. 



A second point of considerable interest is the apparent isolation of many of tk 

 spermatic sacs, and the probability that they arc not diverticula of the spermatic duct 

 but, secondarily, in the course of their ripening acquire a connexion with it, the twe 

 structures having developed independently. This is in accordance with what is knowr 

 as to the essential nature of the genital ducts of Arthropoda, although it cannot be saic 

 that we have, at present, a sufficient series of observations upon their development tc 

 warrant a generalization. 



DESCRIPTION OF PLATE XXXVIII. 



Fig. 1. The carapace lias been removed from the cephalothorax (Ceph), and the tergum from the 

 abdomen (;lbd), to show the course of spermatic network amongst the liver (//'), which is not 

 indicated: A, median network ; L, lateral network ; Cx l -Cx°, coxo-tcrgal muscles, the rounded 

 knobs (k) to which these are inserted are parts of the cntocoxites of the appendages ; Br.lh, 

 branchio-thoracic muscle ; I) 1 , J) r , the hit and right main sperm-ducts, dipping down to the 

 external aperture in appendage vii. 



Fig. 2. Genital operculum, half nat. size. Posterior face, to show the papillae in which the external 

 apertures of the genital duct arc situated ; gen, d, sperm-duct dividing into three main branches ; 

 g.p, its external aperture; Stg, stigma; t.s, tendinous stigmata; ant., anterior lamellar 

 muscle; ext., external branchial muscle. 



Fig. 3. Portion of the median network A (fig. 1), magnified about £H times; AA, lateral boundaries of 

 this portion ; d, duct ; sp, sperm-sacs. 



Fig. 4. Mature spermatozoa. 



Fig. 5. Portion of a section showing sperm-sacs, x 22 : d, sperm-duct ; W, wall of duct ; L, epithelium 

 of duct; -S, aggregations of spermatozoa ; c, surrounding connective tissue; M, membrane of 

 sperm-sac ; B, sperm-sac with no apparent connexion with duct. 



Fig. 6. Portion of wall of sperm-duct, seen from without ; enlarged about 39 times. 



Fig. 7. Transverse section of duct, x39: d, lumen of duct; L, epithelium; n, nuclei; W, wall; S, 

 spermatozoa within the duct. 



