576 THE AMERICAN NATURALIST. [VOL. XXXV. 
habit, etc. ; but a closer scrutiny will reveal so intimate a 
fundamental likeness in all essentials as to demonstrate clearly 
the homological equivalent of every feature, some of the acces- 
sory or sensory structures alone excepted ; and since these are 
not constant features they may clearly be disregarded in the 
comparison. Differences as to form and habits may be con- 
sidered as adaptations to the characteristic functions of a free 
and motile organism. 
In keeping with the synopsis of orders already given, that 
of the several families and genera of Medusz will be taken up 
in their respective order. 
ANTHOMEDUSZE. 
The Anthomedusz are generally of more or less hemispheri- 
cal form or sometimes of an elongate or subconical outline. 
All are possessed of a definite, muscular velum ; sensory 
organs or ocelli borne on bulbs located at the bases of the 
tentacles, about which there is usually a colored pigment ren- 
dering them quite conspicuous, are usually present ; otocysts are 
not present. The radial canals are generally four in number, 
rarely six or eight; gonads are developed and borne on the 
walls of the manubrium. 
SYNOPSIS OF FAMILIES. 
I. Copontp&. Mouth-opening simple, devoid of tentacles or lobings ; 
gonads not radially divided, but forming a circular, continuous tissue à 
the manubrium ; marginal tentacles-unbranched. 
II. Trarmp#. Mouth-opening provided with simple or frilled oral 
lobes; with four or eight distinct manubrial gonads; marginal tentacles 
unbranched. 
III. MARGELID#. Mouth-opening surrounded with four or more ym 
or branched oral tentacles; four or eight manubrial gonads ; margin 
tentacles unbranched. 
IV. CLADONEMIDA. Mouth-opening rarely simple, usually provided 
with oral lobes or tentacles; marginal tentacles variously feathered °F 
branched. 
