II. 
METAMORPHOSIS AND MORPHOLOGY OF CERTAIN 
PHYLLOPOD CRUSTACEA. 
■ [Plates V— VIH and Plate X.] 
The group Phyllopoda is one of the most remarkable among crusta- 
ceans, on account of the peculiar form and life history of most of its 
members. About the animals of this group there clings a certain air 
of mystery which may lead one to regard them as almost uncanny.” 
A pool by the wayside is suddenly formed by a shower and almost in- 
stantly becomes populated with a swarm of animal life, which no one 
ever saw there before and for the like of which we might search an 
hundred miles in vain. In a few days the little tragedy is played and 
the uncouth actors have disappeared, no one knows whither, having 
sown the clay at the bottom of the now dry pool, with eggs which, 
under favorable circumstances, may again put the play on the boards, 
but only after being themselves thoroughly dried by the sun. In 
short, in the study of these animals the unexpected is always appear- 
ing and known laws, or at least theories, are again and again negatived. 
We calmly institute a species when, lo ! the change in certain condi- 
tions attending the development occasions the change to an entirely 
different genus in our system. 
(See V. Siebold, in Sitzungsberichte d. math.-phys. Classe zn Muenchen^ 18735 ^‘i^l 
the paper by Schmankewitsch in the Zeitschrifi fuer Wissenchaftliche Zoologie, XXV 
Suppl., 1S75.) 
In spite of many able papers and works on American Phyllopods 
(notably the monograph, by Prof. Packard, in The Geol. Siirv. Terj\^ 
1868, Part I ^ Sec. 2.) many points of deepest interest remain to be 
cleared up, and particularly such as relate to the development history 
and homologies of organs. In the present paper a few observations 
made some years ago, are presented with no attempt to discuss their 
bearing upon the questions in dispute. The student conversant with 
the literature of this subject will observe, however, that these facts 
