HYDROID.E: SARSIM:. 513 



shell, or in appearance like little tufts of moss, or minia- 

 ture shrubs, the careless observer might well mistake the 

 fact of their animal character.* But, thanks to learned, 

 persevering, and patient investigators, we know much of 

 their curious and wonderful history. We now know that 

 these little vegetable-like, but acalephian forms produce 

 medusae buds which expand into genuine medusae, and 

 in some kinds sever their connection, and float away and 

 lead an independent life, and in other kinds remain at- 

 tached to the hydroid stalk, and in both cases produce 

 eggs which serve to establish new communities of hy- 

 droids, like the ones from which they themselves were 

 developed. Thus the hydroid communities, and certain 

 medusae, are alternate generations of the same beings. 



The Sub-Order Tubulariae comprises hydroid acalephs 

 in which the medusa is free or persistent, deep bell-shaped, 

 the hydra pedunculated, and the head club-shaped. 



SARSID.E. This Family, as restricted by Agassiz, em- 

 braces those in which the medusae are deep bell-shaped, 

 and have four long tentacles, and a long simple proboscis 

 upon which the eggs are developed. 



The Genus Coryne, formerly Sarsia, is a well-known 

 representative of this family. Fig. 501 shows thevform 

 of one species of Coryne in the adult state. Nothing can 

 excel the delicacy of the structure of these animals. Soft 

 as jelly, transparent as the dew-drop, almost as perish- 



* Of the sub-orders alluded to above, one is Tabu- Jig. 49 8. 



late, whose representatives produce solid parts known 

 as Coral, and formerly referred to the next class, which 

 is the principal coral-producing group. The Genera 

 Millepora, Seriatopora, Favorites, Heliopora, and Fo- 

 ci 'ilopora are now included in this sub-order. In the 

 corals referred to Tabulate, the cells have a horizontal 

 partition or floor extending from wall to wall ; and 



these floors are formed one above another as the animal 



Acalephian Coral, 

 grows ; and the radiating partitions never extend verti- p oc iu op0 ra.c<*spitosa t 



cally through the successive floors. Dana. 



22* GG 



