36 PROCEEDINGS OF THE ACADEMY OF 



widely separated in time into juxtaposition, perceptible differ- 

 ences no doubt would be noticed. Allowing for variation at the 

 ordinary rate of increase, during the immensity of time that has 

 elapsed since the Jurassic tineid flourished, the contrast would 

 be astounding. While variation progresses in some species of 

 animals l>3 r the constant addition of infinitesimally small in- 

 crements, which are seen after the lapse of indefinite periods of 

 time, there are other species which have maintained their own 

 with comparatively kw and trifling changes of character, from the 

 early dawn of Silurian times down to the present moment. The 

 Terebratula of our seas, closely resembles its most distant kin. 

 Whj r maj r not the line which has terminated in our typical Tineids, 

 have been marked by a similar uniformity of structure and habits? 

 Other lines of growth may have led from these ancient Tineida 

 to our highest types of cocoon-builders, through which in course 

 of time our butterflies and sphinges were evolved. 



If, as has been previously remarked, the habit of cocoon-building 

 originated in the necessity of the times, as a means of protecting 

 the builder against undue moisture, rather than a low degree of 

 temperature, then we should expect to meet in the history of those 

 early times, some confirmatory facts which would add further 

 links to the chain of argument which has been assumed to prove 

 that the line of development has been from Nocturnal lepidoptera 

 to Diurnal. 



Respecting the climate which prevailed upon the globe when 

 the Jurassic tineid and Sphinx flourished, no facts associated 

 with the geographical distribution of species have been ascertained, 

 that uphold the idea of a diversity of zones, such as now exists. 

 The facts sustain the view that the climate of the Arctic during 

 this period was at least warm-temperate. The presence of Belem- 

 nites paxillosus and Ammonites biplex, or some closely-related 

 species, according to the authoritj' of Dana, in the Arctic, the 

 Andes of South America, and Europe, indicates a remarkable uni- 

 formity of climate over the globe. 



The character of the plants which then existed affords a cogent 

 reason for believing that a moist climate prevailed. Experience 

 has taught us that Conifers and trees allied to Yucca and Bro- 

 melia, Equiseta and Ferns, do best where the soil possesses much 

 moisture and the climate is uniform. The gigantic Conifers of 

 Western North America, and the tree-ferns of the East, attain 



