Introduction to Animal Morphology. 



103 



Two orders are included herein : — 



I. Rhizostomida — Reproductive organs in free 

 zooids, with no marginal tentacles nor Fig. 14. 



central mouth, but with a tree-like 

 mass depending from the umbrella, 

 bearing many, mouth-like openings, 

 formed by the irregular gaps produced 

 by the contact and adhesion of com- 

 plexly folded oral lobes. 



In this order, and the next, thej^i^^^i^^ibodyofchaby- 



1 ' ' £ ^-L daea marsupialis, show- 



young embryo on emission from the ing its staik cavity, two 



, 1 /T^. T\ 1 • 1 lenticular bodies (eyes). 



^g'g" IS a planUla (rig. 15, <?), which, and one lithocyst below. 



after a short locomotive period, attaches itself by its 



narrow end to some solid body, and forms a mouth 



and stomach by invagination at its distal end, around 



which four rudi- 



mental tentacles 



develop (15, c) \ 



these elongate, and 



others form in their 



intervals. This 



hydra-like form 



lengthens, its 



mouth extends into 



a manubrium-like 



_._^„„„„ ■-i-nA 1/~,n ^, Aurc lia aur ta ; i, development of Aurelia aurita, 

 process, ailU 1011- p,,^nuia; c, n^dra tuba; d, Hydra tuba budding; 

 critnHinal ranaK *"' Scj-ptistom a;/, Strobila; g, Ephyra; /, tentacles; 



glLUiaiiidi i^ctiidis „i 3 marginal bodies ; c. c. circular canal. 



sketch from the mouth to the wall of the body. 



This trophosome having lived for a variable time 

 [c.d.)^ the elongated wall of the hydra tuba (as it is 

 called) becomes marked by a series of transverse 

 grooves [e] around its circumference, which deepen, 

 dividing the tube into a series of superposed discs, like 



