Mat 6, 1910] 



SCIENCE 



715 



reached the stage of the fully developed 

 pluteus. Later stages of young echinoderms 

 were obtained in tows. The eggs of Tur- 

 riiopsis developed through the planula stage. 

 Eggs of Chwtopterus and Thalassema were 

 artificially fertilized. 



Mr. George W. Comer, 3d, medical student 

 at the Johns Hopkins University, Baltimore, 

 Md., spent the months of July and August 

 collecting and studying the invertebrates. 

 Henry D. Aller, 



Director 



SPECIAL ARTICLES 



PRELIMINARY NOTE ON THE LIFE OF GLACIAL 

 LAKE CHICAGO 



Excavations made for the new sanitary 

 canal, which will extend from Willmette to 

 the North Branch of the Chicago River at 

 Bowmanville, have disclosed a series of beds 

 filled with organic remains which reveal very 

 fully the characteristic faunas of the several 

 stages of glacial Lake Chicago. The cut at 

 the Bowmanville end of the canal is a mile 

 long; the depth is about twenty-five feet, 

 fifteen of which are in boulder clay (glacial 

 till) undisturbed by water action. The upper 

 ten feet are composed of alternate layers of 

 sand, clay, peaty material and shell beds. 

 These strata quite fully portray the biologic 

 history of the lake. 



The area through which the canal is cut 

 lies behind (west of) the Rose Hill bar and 

 the strata exihibited in section were succes- 

 sively the bed or floor of Lake Chicago. These 

 strata may be described as follows : Above the 

 till there is a bed of sand from two to twelve 

 inches in thickness. This doubtless repre- 

 sents the Glenwood stage and, as would be 

 expected, no life is present. Above the sand 

 is a bed ten to eighteen inches thick, com- 

 posed of clay mixed with peaty matter, logs 

 of wood and leaves of trees (oak and spruce). 

 MoUuscan shells of the genera Planorbis, 

 Physa, Lymncea, Ancylus, Sphcerium, Pisid- 

 ium and Amnicola abound. The presence of 

 this extensive deposit, which can be traced the 

 entire length of the canal, beaeath deposits 

 unquestionably of Calumet time, strongly sup- 



ports, if indeed it does not prove, the early 

 contention made by Dr. Andrews of a post- 

 Glenwood low-water stage. The species of 

 mollusks are mostly those found in swamps 

 or along the edges of shallow bays or lakes. 



Above the clay is a deposit of sand and 

 gravel, two to nineteen inches in thickness, on 

 the surface of which is one of the thickest 

 beds of naiades the writer has ever seen. 

 There are upwards of a dozen species, in- 

 cluding Unio gibhosus, U. crassidens, Quad- 

 rula undulata, Q. rubiginosa, Q. trigona, Q. 

 verrucosa and Q. pustulosa. With these are 

 associated Campeloma, Sphcerium and Oonio- 

 hasis. The shells are species which frequent 

 large streams of more or less rapidly flowing 

 water, as the Illinois and Mississippi rivers, 

 which fact, together with the unassorted char- 

 acter of the sand and gravel, shows that there 

 was a rapid flow of water from the lake to the 

 Desplaines outlet behind the Rose Hill bar. 

 This deposit is believed to represent the Calu- 

 met stage. The presence of Unio crassidens 

 is of great interest, as this species is not now 

 found north of La Salle County in Illinois. 



Above the Naiad deposits there are alternate 

 beds of clay and sand, with occasional pockets 

 of shells, the aggregate thickness being about 

 thirty-two inches. The presence of peaty 

 matter and wood afford evidence of a second 

 low-water stage. In one of these deposits the 

 humerus of a small bird was found as well as 

 several fish spines. 



Above this deposit there is a bed of mol- 

 luscan shells forming a compact mass from 

 one and one half to five inches in thickness. 

 These are of swamp or bay species of the 

 genera Lymnwa, Planorhis, Physa, Valvata, 

 Campeloma, Amnicola, Sphoerium, Pisidium, 

 etc. Naiades are uniformly absent. This 

 deposit was formed during the early portion 

 of the Toleston stage, when the area behind 

 the Rose Hill bar formed a reed-bordered bay. 

 Above the shell bed is a deposit of clay seven 

 to twelve inches in thickness, and above this, 

 a typical peat deposit three and one half to 

 eight inches in thickness. This deposit was 

 formed in a small lake or pond, as it is of 

 small extent. The region at this time was of 



