2o8 KIXGSLEY. [Vol. VIII. 



That these organs in Limulus and Arachnids are homologous 

 admits of little doubt. It is scarcely more doubtful that they 

 belong to the same category as the antennal glands and shell 

 glands of the Crustacea. The correspondence, as I earlier 

 pointed out, is exact between the coxal gland of Limulus and 

 the shell gland of the Entomostraca. Their closure in Limulus 

 and certain arachnids is paralleled for instance in the case of 

 Argulus (teste Leydig, BS), where the shell gland is functional 

 only in early life. On the other hand, as stated above, the 

 coxal gland in Phalangids is functional in the adult. 



In the light of recent investigations these organs must be 

 regarded as nephridia, and the arguments to the contrary 

 advanced by Eisig ('88) are without foundation. Two recent 

 studies are of interest here : That of Sedgwick on the develop- 

 ment of the nephridia in Peripatus, and those of Weldorr ('89 

 and '9i) on the relations of the antennal gland to the coelom in 

 the Decapods. In Peripatus the development is strikingly like 

 that in Limulus, except there are numerous pairs of nephridia 

 in the former. In both there is the formation of small coelo- 

 matic spaces ; in both {cf. Kishinouye, '91^) a division of the 

 coelom into dorsal and ventral portions, and in both thcicon- 

 version of the ventral coelom into end sac, nephrostome, duct, 

 and bladder. It is interesting in this connection to note that 

 according to Loman ('87) in Phalangium, where the nephridial 

 opening does not close and the organ remains functional 

 through life the Malpighian tubes — the other urinary organs 

 — are lacking. 



I am inclined to believe that the genital ducts of Limulus 

 are also to be regarded as nephridia, but I have searched in 

 vain for any trace of their development. Laurie's account of 

 the origin of the ducts in the scorpion is, as he says, intelligible 

 upon the ground that they are nephridia; their somewhat tardy 

 appearance and lateness in opening to the exterior not seriously 

 militating against such a view. 



Muscles. — I have not attempted to trace the history of the 

 muscles except to a slight extent. The muscles, which move 

 the feet and which extend from the dorsal surface of the body 

 down to the appendages, are developed along the intcrseg- 



