862 The Arthropod Eye. [ October, 
early days, would have taken different directions. But the fol- . 
lowing out of these subjects is not within the province of a geo- 
logical paper. 
NorTeE,—Since the above paper was written I have been favored by the courtesy 
of Mr. O. Guthrie, of Chicago, with a copy of the Report of the Committee on the 
Drainage of Chicago, and a letter containing some further interesting details upon 
t 
the subject, From these data I learn that the low ridge be oD Chicago, mentioned 
in the above paper, has a breadth of only five miles, and that a scheme is on foot for 
Ady cutting a canal or a channel through it to the Des pass river in order to carry 
away the sewage of the city entirely from L. Michigan, and avoid the contamination 
of the water-supply, whose purity is now seriously endangered by the flow of drain- 
/ age into the lake not far from the crib, during floods in the Des Plaines river. 
BS. | THE ARTHROPOD EYE. 
BY Jj. S. KINGSLEY, SC.D. 
1 idee year 1886 has already seen several important studies 
rally al altered our conception of the organ and of compound vision. 
Of these studies by far the most important are those detailed 
in Dr. William Patten’s “Eyes of Mollusks and Arthropods” 
ee zool., Stat. Neapel, vi, pp. 542>756. pls. XXVINI-XXXII, 
: e paper is far too long for complete abstract here, 
= pur some of the more important points relative to the compound 
eye may be useful in supplementing the statements in the manuals 
of comparative anatomy. Incidentally it may be remarked that 
the matter pertaining to the eyes of mollusks is equally valuable. 
As described in our hand-books, our knowledge of the eyes © 
: Crustacea, spiders and insects is based on Grenacher’s classic “ Se- 
1organ der Arthropoden ” (1879), and no one (Graber Berar 
ıs ventured to criticise his results. Not so Dr. Patten. He has 
shown that Grenacher is wrong in many fundamental points, aod 
that his conception of these organs is in some respects so erroneous 
as to be all but worthless. The writer, in passing, may remark that 
> has had occasion, in studies in a somewhat different direction, 
verify many of Patten’s statements, and so far as he has gone 
upon the eyes of Arthropods, some of which have mate- 
can confirm them. The figure of one of the elements of the 
: = ~ emp illustrating this article, is drawn from his own- . 
ations, but in all essential features it agrees well with simi- : 
the eyes of other Crustacea given by Patten. The» 
wee 
