THE AMERICAN NATURALIST [Vol. XLII 



the summer, and one female under observation furnished 

 four successive ones (all made in the night) ; they hatch 

 on the twenty-fifth or twenty-sixth day. Marmorea does 

 not construct cocoons until the fall. Comparisons were 

 made on the following points: (1) number of radii, (2) 

 number of spiral loops, (3) greatest diameter of the spiral 

 (orb proper). The spiral loops examined are those of the 

 outer viscid spiral which is the true trap of the web, and 

 the number of its turns were counted in that segment 

 of the orb where they "were most numerous (generally in 

 the region below the central hub). A slight error is some- 

 times encountered in counting these loops for occasionally 

 the innermost of them are scarcely distinguishable from 

 the inner non-viscid spiral, but this is an error of only 

 small amount. 



The following table gives in condensed form the meas- 

 urements of 265 snares. On the left is entered the spe- 

 cies, sex and age, the linear measurements are in centi- 

 meters, the remainder is self-explanatory. 



111! 



3.2 86 lS.o-18.3 



41.3 16 14 -30 

 3 19.6-25.4 



With regard to increase of complexity of the snare 

 with advance of age of the spider this table shows us the 

 following figures for sclopetaria. The first formed 

 snares, those of the newly hatched, exhibit an average 

 of 15.3 radii, 16.2 spiral turns and 7.6 cm. diameter in 

 comparison with averages of radii, 35.4 spiral turns 



