No. 3-] LIMULUS POLYPHEMUS. 46 1 



The embryos were stained in toto with Delafield's haema- 

 toxylin or with borax carmine, followed by Lyon's blue on the 

 slide. The larvae and young Limuli were treated with Dela- 

 field's haematoxylin, and picro-acid fuchsin, or eosin. 



The nephric duct may be injected by forcing a canula into its 

 external opening at the base of the fifth leg, or it may be liga- 

 tured into the end of the duct, just below the shell. 



Starch masses, or a thick celloiden mixed with lamp black, 

 were used for injections. After celloiden injections are hardened 

 in 80^0 alcohol for several days, the connective tissue may be 

 dissected away from the duct, and its course followed without 

 much difficulty. Complete casts of the duct may be obtained 

 by maceration in strong hydrochloric acid ; but in all cases the 

 casts which were made showed a good deal of shrinkage. A 

 good starch, asphalt, or celloiden mass will completely fill the 

 duct and penetrate deeply into the nephridial lobes. 



III. Critical Review. 



The Nephridia of Limulus were first described by Packard 

 in 1875, who concluded that they were renal organs, compa- 

 rable with the green glands of Crustacea. In 1880, he com- 

 pared them with the shell glands of th-e Entomostraca. 



Lankester described them in 1880, and later ('82) discussed 

 their histological structure in detail, comparing them with the 

 coxal glands of scorpions and Mygale. Both Packard and Lan- 

 kester saw only the lobes and the longitudinal stolon of the 

 adult, and entirely overlooked the large thin-walled duct and its 

 external opening. Packard tried to find a duct by injecting the 

 gland, but failed. In 1895 Tower discovered the opening of 

 the gland in the adult in the interarticular membrane on the 

 posterior side of the base of the fifth leg. It is situated, as he 

 correctly states, on a papilla, readily seen with the naked eye, 

 and surrounded by a dark gray ring. 



Gulland (-85) and Kingsley ('85 and '93) gave an incomplete 

 description of the embryonic duct and its relation to the fifth 

 coelomic cavity. They were deceived, however, in mistaking 

 the developing duct and its end sac for the developing nephric 



