25 MANUAL OF ZOOLOGY. 



their bodies which they may have lost. Thus, the Crustacea 

 possess the power of reproducing a lost limb, by means of a 

 bud which is gradually developed till it assumes the forai and 

 takes the place of the missing member. In these cases, how- 

 ever, the process is not in any way generative, and the pro- 

 duct of gemmation can in no sense be spoken of as a distinct 

 being (or zooid). 



Another form of gemmation may be exemplified by what 

 takes place in the Foraminifera, one of the classes of the 

 Protozoa. The primitive form of a Foraminifer is simply a 

 little sphere of sarcode, which has the power of secreting from 

 its outer surface a calcareous envelope ; and this condition 

 may be permanently retained (as in Lagena). In other cases 

 a process of budding or gemmation takes place, and the prim- 

 itive mass of sarcode produces from itself, on one side, a 

 second mass exactly similar to the first, which does not detach 

 itself from its parent, but remains permanently connected with 

 it. This second mass repeats the process of gemmation as 

 before, and this goes on — all the segments remaming attached 

 to one another — until a body is produced, which consists of 

 a number of little spheres of sarcode in organic connection 

 with one another, and surrounded by a shell, often of the 

 most complicated description. In this case, however, the 

 buds produced by the primitive spherule are not only not 

 detached, but they can only remotely be regarded as independ- 

 ent beings. They are, in all respects, identical with the prim- 

 ordial segment, and it is rather a case of " vegetative " repeti- 

 tion of similar parts. 



Another form of gemmation is exhibited in such an organ- 

 ism as the common sea-mat (Flustra), which is a composite 

 organism composed of a multitude of similar beings, each of 

 which inhabits, a little cliamber, or cell ; the whole forming a 

 structure not unlike a sea-weed in appearance. This colony is 

 produced by gemmation from a single primitive being (" poly- 

 pide "), which throws out buds, each of which repeats the pro- 

 cess, apparently almost indefinitely. All the buds remain in 

 contact and connected with one another, but each is, neverthe- 

 less, a distinct and independent being, capable of performing 

 all the functions of life. In this case, therefore, each one of 

 the innumerable buds becomes an independent being, similar 

 to, though not detached from, the organism which gave it 

 birth. This is an instance of what is called " continuous gem- 

 mation." 



In other cases — as in the common fresh-water polype or 

 Hydra — the buds which are thrown out by the primitive or- 



