Birge and Juday—Development of Cyclops . 9 
which constitutes the cement of the cocoon. Certain crustace* 
regularly secrete such a substance; among them, Holopedium 
one of the Cladocera. S'o far as we are aware, no such sub¬ 
stance has been found secreted by a Copepod. The tissue 
changes during the four months of encystation constitute 
another subject on which nothing has been done; nor is 't 
known whether or not the encystment is accompanied by 
moulting. 
So far as the authors know, this is the first case of this kind 
reported from the Copepoda. It opens a new and interesting 
field of research into the adaptations of Crustacea to the dif¬ 
ferent biological conditions offered by inland lakes. 
REFERENCES. 
E. A. Birge, ? 97: Plankton studies on Lake Mendota, II. 
Trans. Wis. Acad. Sci., Arts and Letters, xi: 274-448. 
42 plates. Madison, 1897. 
C. Dwight Marsh, ? 03: The plankton of Lake Winnebago and 
Green Lake. Bull. Wis. Geol. and Nat. Hist. Survey ., no. 
xii. Pp. vi+94; 2'2 plates, Madison, 1903. 
O. Schmeil, ? 92: Deutschlands freilebende Siis^wassercope- 
poden, Teil 1. Pp. 191; 8 plates. Cassel, 1892. 
