58 INVERTEBRATE ANIMALS. 
it is not uncommon for the same individual to produce both 
of these elements, in which case the individual is said to be 
‘‘hermaphrodite.” Amongst the lower animals, however, fresh 
beings may be produced without the contact of a sperm-cell 
and an ovum,—that is to say, without any genuine act of 
reproduction. The processes by which this can be effected 
in different animals vary considerably, but they are all spoken 
of as forms of “non-sexual” reproduction. The only varieties, 
however, of the process which require consideration, are those 
in which fresh beings are produced by what is called “ gemma- 
tion ” or “ fission.” 
Gemmation (Lat. gemma, a bud) consists in the production 
of a bud or buds, usually from the outside, but sometimes from 
the inside of an animal; which buds become developed into 
more or less completely independent beings. The fresh beings 
thus produced by budding ,are all known as zodzds, and are 
not spoken of as distinct animals for reasons which will be 
immediately evident. When the zodids produced by budding 
remain permanently attached to one another and to the parent 
organism which produced. them, the case is said to be one of 
“continuous” gemmation, and the ultimate result of this is 
to produce a colony or composite structure, composed of a 
number of similar and partially independent beings, all pro- 
duced by budding, but all remaining in organic connection. 
This is seen very well in the sponges, in the compound fora- 
minifera, and in a great number of the Hydrozoa. When, on 
the other hand, the zodids produced by budding become finally 
detached from the parent organism, we have a case of what is 
called “discontinuous” gemmation. In this case, the detached 
zodids become completely independent beings; and they are 
often wholly unlike the original zodid in structure and in 
habits, so much so that they have in various cases been de- 
scribed as altogether distinct animals. Discontinuous gemma- 
tion is very well seen in many of the A’ydrozoa, and in them 
the case is still further complicated by the coexistence of dis- 
continuous gemmation with the continuous form of the process. 
Thus, it is not an uncommon thing amongst the Hydrozoa to 
find a composite organism or colony produced from a primordial 
zooid by continuous gemmation, and having at the same time 
the power of giving rise to detached and completely indepen- 
dent beings by a process of discontinuous gemmation. 
