ANCESTRAL SPIDKRS AND THEIR HABITS. 461 



of Tlieridiosonia geimnosum that it is pyriform, pediculated, of yellow 

 brown color, with pedicle white, and that the female makes her cocoon at 

 the end of June.' This description well agrees with the cocoon under 

 question. Simon himself says that Thcridiosoma gemmosum is found 

 along the borders of waters, making its snares upon aquatic plants. Its 

 cocoon is in the form of a balloon, witli a pedicle like that of Ero.'^ As 

 Theridiosoma gennnosum and T. radiosum are probably identical, or at least 

 closely related, this evidence appears to be almost conclusive. 



I have measured many of these Theridiosoma cocoons, and they aver- 

 age in length about one-eighth inch, or, more accurately, three and one- 

 half millimetres. Their width is a little less. In other words, the cocoon 

 is almost spherical, but the addition of the pedicle or stalk makes it seem 

 longer. I have seen some cocoons which were five millimetres long. The- 

 ridiosoma's cocoons are closely woven and of tough fibre, well fitted for 

 preservation. If now we compare the above named structures with Scud- 

 der's fossil cocoons, we shall find a close resemblance. We may therefore 

 have little hesitation in relegating Aranea columbite to some such The- 

 ridioid genus as Ero or Theiudium, or perhaps to the ancestors of Therid- 

 iosoma. The Ray spider has evident relationship to Theridium, as appears 

 from the fact that such accomplished araneologists as Cambridge, Simon, 

 and the late Count Keyserling have classed it with the Retitelaria?. One 

 might therefore venture to attribute to it an ancient lineage, and even to 

 risk the conjecture that a species of Theridiosoma may liavc been the au- 

 thor of some of Scudder's fossil cocoons. 



The preservation of any spinningwork through so vast a period is 

 greatly interesting ; but I find tlic chief value of the fact in the inference 

 that the general habits of spiders have followed even more 

 Unmodi- dosely the law of unmodified survival that appears to mark 

 fled In- ^j^^ general structure of araneads. Indeed, I am not able here 

 to note any difference. Precisely the same industry that we see 

 everywhere exemplified in the pretty hanging basket cocoonery of our 

 modern Ero, Theridium, or Theridiosoma, characterized the fossil Aranea 

 columbioe that wrought her spinningwork along the shores of Lake Flor- 

 issant in the early period of the Tertiary. It is certainly not an unwar- 

 ranted inference that the spinning organs by which these cocoons were 

 produced differed in no essential particular from those possessed by mod- 

 ern spiders.^ This likeness implies structural similarity in other vital 

 organs, and hence, reasoning from industrial product to function, from 

 function to organ, from special organs to general structure, we arrive at 

 the same conclusion that seems justified by a study of Scudder's Ameri- 

 can fossils, that many spiders of the Tertiary were not widely diiferent 



' Simon, Arach. de France, Vol. V., page 27. * Ibid., page 25. 



» See Vol. I., Cliapter II. 



