1903.] NATURAL SCIENCES OF PHILADELPHIA. 131 



while the diversity of embrace in the web-making species may be in 

 part due to differences in the web construction, in part to degree of 

 sexual dimorphism. The Epeiridcc and Theridiidce show the greatest 

 diversity of embrace, and in these families is to be found also the great- 

 est sexual dimorphism. In other words, the mode of embrace may be 

 brought into more or less conformity with the general mode of life of 

 the species. Similarity of embrace points, then, to similarity of 

 other habits, but not necessarily to community of descent. No spider 

 shows the attitude of embrace common among insects, namely the 

 male above the female with his head pointed in the same direction as 

 hers. 



Details of the Process of Copulation. — The following table combines 

 data of the other observers with my own upon the details of copula- 

 tion. Where a species has been entered more than once, each repeti- 

 tion denotes a separate act of copulation. In the column "Duration 

 of Copulation," h, m, s, signify hour, minute and second respectively. 

 In the column headed ''Simultaneous," the sign X denotes that both 

 palpi are inserted at once, and the sign — that they are not. In the 

 column headed "Alternated," the sign X indicates that the right and 

 left palpi are inserted alternately, but that the number of alternations 

 was not noted ; the sign — ,that only one palpus is employed ; while a 

 number expresses the number of alternations of the right and left 

 palpi. In the columns headed " Right Palp" and " Left Palp," a num- 

 ber enclosed in brackets denotes the average number of times one pal- 

 pus is inserted successively before the other palpus is inserted, 

 this average being obtained by dividing the total number of in- 

 sertions of that particular palpus by the total number of alternations 

 of the palpi. Spaces left vacant in the columns denote lack of 

 observations. For the great number of small details that cannot 

 be reproduced in such a table, the reader is referred to the obser- 

 vational part of this paper, and to the works mentioned in the 

 literature list. 



