2 THE ZOOLOGIST. 



Some observers and many writers draw hard and fast distinctions 

 between budding and fission (binary, cross, longitudinal, and 

 diagonal). The former (budding) is said to occur — for instance, 

 in the simplest animals — when the portion separated is smaller 

 than the parent, the latter (fission) when it is about the same 

 size. Again, in an animal with a linear series of segments, the 

 term budding is applied to those instances in which from one or 

 two segments a complete animal with head and internal organs 

 is formed ; while fission is said to take place in those cases in 

 which a considerable number of the adult segments are cut off 

 to form the new animal, the diameter of which is thus more 

 nearly that of the parent-stock. But it is clear that if in the 

 latter case a new head, brain, and sense-organs are developed 

 out of an ordinary segment, it also is more or less an example of 

 budding. 



In dealing with certain divisions of the subject, however, 

 more precise terms are employed. Thus, for instance, in the 

 Marine Annelids, the terms " schizogamy " and " scissiparity " 

 are generally used. 



In schizogamy (Syllids, &c.) a part of the individual only 

 acquires ova or other elements, and separates. The head of the 

 bud has large eyes, but no mouth, and only serves to disseminate 

 the ova or other elements, and then disappears. No new pro- 

 ducts are formed. Scissiparity (fission) differs from schizogamy 

 in so far as it is a veritable multiplication, the two (parent and 

 bud) resembling each other, and developing either ova or other 

 elements independently. 



In the lowest group of animals, the Protozoa, simple division 

 of the body is very common, but in many (e. g. Arcella and 

 Pelomyxa), after conjugation, numerous buds, which are smaller 

 than the parent, are given off at once. Moreover, in such as 

 Codosiga, a colony is formed by budding, and, as in this and 

 other instances the buds do not separate, the branching struc- 

 ture resembles a miniature zoophyte. 



In these simply organized animals budding would appear to 

 be the most natural method of increase, the buds either remain- 

 ing separate and gradually attaining the bulk of the original, 

 or, as in Codosiga, developing into a continuously branched 

 organism. As true eggs are unknown in the group, there can 



