OF DENISON UNIVERSITY. 1 7 



make necessary a modification of views at present in vogue in several 

 important particulars. The work was arbitrarily closed by circum- 

 stances and the material was long suppressed, in the hope of continu- 

 ing a study which proved of absorbing interest ; but, as this hope is 

 now extinct and no motive remains for further delay, the observations 

 are presented in their necessarily fragmentary form, hoping to fill a 

 place in the life -history of these remarkable animals. 



The Phyllopoda are extremely well adapted for use in biological 

 laboratories and the outline here given may make the process of de- 

 velopment plainer to the student who is fortunate enough to be sup- 

 plied with such material for study. The two animals described may 

 be found in early spring and late summer, in many temporary pools 

 throughout the eastern zoographical province of North America. 



A. Larval Develop7nent of Limjietis gouldii, Bd. 



Liinnetis is a genus of the Family Limnadiad^ of Baird, which 

 includes crustaceans enclosed in a bivalved shell, within which is con- 

 cealed a body like that of a Water Flea, but having ten to twenty- 

 seven pairs of leaf-like swimming feet. The very large head projects 

 from between the valves in front and is flanked on either side by a 

 b'iramose second antenna, while the first pair of antennae is very small. 

 A figure of the adult of the present species will be found in the mono- 

 graph by Dr. Packard, and also in a paper by the present writer, in the 

 loth Annual of the Minnesota Geological Survey. 



The earliest stage seen (Plate VI, Fig. 2.) was the simple nauplius- 

 form common to all this group of Crustacea, but so curiously modified 

 as to at first almost defy recognition. The animal, as viewed from 

 above, seems covered almost entirely by an oval shield, which is thickly 

 studded with spines arranged in anastomosing lines. The head ex- 

 tends into a frontal prominence, which is densely bearded. The pos- 

 terior part of the body forms a blunt prominence, bearing two spines. 

 The eye, occupying the front of the head, consists of a single pig- 

 ment fleck, with at first a single lense (?). The digestive tract is 

 simple and similar to that of other Phyllopod larvae. In the protu- 

 berance which represents the future abdomen, the muscles producing 

 the pumping action of the rectum are well developed and anal respi- 

 ration at once begins. 



The appendages differ only in form from those of other larvas. 

 The antennules are long and curved prolongations of the frontal region 



