250 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



under native trees and shrubbery; in the mud of streams; under rotten and 

 decaying stumps and leaves in the forest; under moss and the rotting seaweeds 

 on the coast. It is in such localities that we must search for our native Oli- 

 gochaeta. 



The large worms are generally the best known; the smallest have been 

 neglected, and it is principally among these latter that we may hope to find 

 new and interesting species. The small white worms so common in the north 

 are but little known; so also are the forms found in the mud of rivers and 

 springs. On the Pacific Coast the native worms are generally of a pale gray 

 or flesh color. The European species are as a rule darker, the reddish or 

 brownish color being due to heavy pigments. 



The reason for the European species supplanting the native forms is prob- 

 ably due to several causes. The former are much hardier and may be easily 

 transported from one locality to another without injury. They are less sensi- 

 tive to heat and light, which is probably due to their pigmentation. As a rule 

 they are adult all the year round, while the native species are adult only in the 

 first half of the rainy season; therefore the European species have a longer 

 breeding season and can better adapt themselves to climatic conditions. The 

 European worms seem to have grown up in the vicinity of man and have 

 accommodated themselves to his cultivation of the soil, which cultivation 

 drives the native worms away. While this refers especially to the worms in 

 our temperate regions, it is also the case in the highlands of Mexico and to 

 some extent in the tropics. The encroachment of the European Terricolae is 

 such that in time there will be few if any native species left. Of the smaller 

 foreign Liniicolide worms, but few seem as yet to have spread in this country. 



It is of the greatest importance when collecting to remember the fact 

 that nearly all earthworms when adult possess a ditferent colored band — the 

 clitellum — on the anterior part of the body. If this band is not present the 

 species cannot be identified. 



Methods of Indicating the Thickened Septa. 



Many investigators satisfy themselves with simply describing some septa 

 as thickened. This, of course, does not indicate the relative thickness, and 

 if it be given in the text much time is consumed in committing it to memory. 

 The following method of indicating the relative thickness of the septa is sug- 

 gested by the author. Septa are to be indicated by Roman numerals, a bar 

 on top indicates that the whole septum is thickened, a bar below indicates 

 that it is thickened only below. One bar indicates twice the thickness 

 of the ordinary septum, and two or more bars indicate increased thickness. 

 "O" in place of the Roman numeral indicates that the septum is wanting. 

 A fraction in front of a numeral indicates that the septum is attached to 

 the center of the somite and does not correspond to the intersegmental 

 groove. For examples of this method the reader is referred to the descrip- 

 tions under species. A single bar may indicate that the septum is as thick 



as two ordinary septa, a bar and a half ( ) may indicate that the 



septum in question is one and one-half times thicker than an ordinary septum. 

 If the septum is thickest in the center, this may be indicated by diminishing 

 the bars toward both ends. 



