1903.] NATURAL SCIENCES OF PHILADELPHIA. 137 



is readily determined on dissection. Tlie fact that Limulus is a true 

 arachnid, and probably a relatively primitive one, allows us to use 

 these peculiarities of structure as a partial basis for explaining the 

 araneid mode of copulation; though the following reasoning would 

 hold equally good, even if Limulus should be left out of the question. 

 The palpal organs of male araneids must have been originally clasping 

 organs, to hold the female. Supposing the terminal joints of the male 

 palpi clasped the female in the region of her genital aperture, around 

 which developed a hard chitinous plate, the epigynum, which would 

 allow a firm hold without injury to the female, then if the original mode 

 of embrace were that where the ventral surfaces of the copulating indi- 

 viduals were apposed, these two suppositions would explain the copu- 

 lation of modern araneids. Depressions in the epigynum would be 

 developed to correspond to projections upon the palpal organs. The 

 surfaces of the palpal organs, which are apposed to one another during 

 the act of clasping, could become in time so modified as to form to- 

 gether a tube to guide the seminal fluid from the genital aperture of 

 the male into that of the female. They would thus change from mere 

 clasping organs to intromittent sexual organs, and then perhaps the 

 other legs come into use as clasping organs, which is their use in copu- 

 lation in modern araneids. Subsequent would be the development 

 of the compHcated tubular apparatus within each palpal organ; and 

 when this were finally developed, the habit of charging the palpi \\dth 

 sperm before the copulation would be involved, and then diversity in 

 embrace and modes of application of the palpi could follow. 



There is still another thinkable mode of origin of the araneid mode 

 of copulation. The pedipalpi might be used, not as claspers in the 

 first instance, but to carry drops of semen during the act of copulation 

 from the genital aperture of the male to that of the female; later, 

 the male during copulation might discharge his semen upon the web, 

 and then take up the semen with his palpi and apply it to the female ; 

 still later, the charging of the palpi with the semen would come to be 

 an act separate from the copulation. 



One or the other of these has been prol3ably the mode of origin of 

 the habit, but which cannot be decided until observations have been 

 made upon the mating of the most primitive Hving araneids, the 

 Tetrapneumones. Very apposite in this connection are the interesting 

 and detailed observations of my friend Heymons* upon Galeodes. 

 In this primitive arachnid the male forcibly seizes the female, holds 



•"'Biologische Beobachtungen an asiatischen Solifugen," Abh. Preuss. Akad. 

 Wiss. Berlin, 1901. 



