THE HYDROMEDUSAE 



A process of budding, similar in character but not followed by 

 a separation of progeny from parent, results in the production of 

 colonial forms (Figs. 16 to 20); in the colony thus formed, the 



Fio. c. 



5.— Section of a medusoifl, plaowl mouth uijwards for coiiii>arison with a hydioid (Fig. 4). 

 Tlie right half of the section is taken alon^ a radial canal, the left half between two radial 

 canals. CC, circular canal ; El\ exninbral surface ; C, ^onad or n''"crative cells lying in the 

 ectoderm of a ])r(X'ess of the subunibral Ixxly wall (characteristic of Leptomedusae) ; G' , 

 gonad lying in the ectodenn of the manubrium (characteristic of Anihoniedusae); 01., gastral 

 lamella ; M, manubrium ; Nil, the outer, and .N7f, the inner jiarts of the nerve ring ; UC, radial 

 canal; SI', subunibral cavity; 7', tentacle; V, velum. Body layers represented as in 

 Fig. 4. 



tJ. — Section of a me<lusoid, at right angles to Fig. 5. Letters as in Fig. 5 ; Ixxly layers as in 

 Fig. 4. 



7. — Diagram showing the chief radii of a medusoid. P, perradii (the first four radii 

 accentuated in development); /, interradii ; A, adradii. 



coelenteron of each hydroid communicates with those of all the 

 other hydroids through the tubular roenosarc or common tissues. 



