^6 KINGS LEY. [Vol. VII. 



appeared. S. Watase has made the structure and development 

 of the visual organs the subject of three papers ('89, '90* '90*'). 

 William Patten ('89) gave a brief note on the origin of the ner- 

 vous system and sense organs, while in a later paper ('90), in 

 which an attempt is made to derive the Vertebrates from the 

 Arachnids, numerous facts relating to the early history of Limu- 

 lus are given. Lastly, I have presented ('90) a brief abstract of 

 some of the results to be described more at length in the present 

 series. 



Habits, etc. 



The American horse-shoe crab {Linmlus polypJienms) is dis- 

 tributed along our eastern shores, from Maine to the West Indies 

 and the Gulf of Mexico (Vera Cruz, teste J. E. Ives), occurring 

 at certain times and places in large numbers. Its habits have 

 been described with some detail by Dr. Lockwood ('70). Dur- 

 ing most of the year it frequents deeper water, but during the 

 breeding season — May until the middle of July — large num- 

 bers come to the shore for the purposes of oviposition. I have 

 never been able to notice any connection between the hours 

 when they frequent the shore and the state of the tide. Sev- 

 eral times on moonlight evenings, in the height of their spawn- 

 il^g season, I have sailed over their favorite spawning grounds, 

 but did not see any of the "crabs." 



I do not know where the couples meet. When first seen they 

 come from the deeper water, the male, which is almost always 

 the smaller, grasping the hinder half of the carapax of the female 

 with the modified pincer of the second pair of feet. Thus fas- 

 tened together, the male rides to shallow water. The couples 

 will stop at intervals and then move on. Usually a nest of eggs 

 can be found at each of these stopping-places, and as each nest 

 is usually buried from one to two inches beneath the surface of 

 the sand, it appears probable that the female thrusts the genital 

 plate into the sand, while at the same time the male discharges 

 the milt into the water. I have not been able to witness the 

 process more closely because the animals lie so close to the sand 

 and all the appendages are concealed beneath the carapax. If 

 touched during oviposition, they cease the operation and wander 

 to another spot or separate and return to deep water. I have 

 never seen the couples come entirely out of the water, although 



