20 COMPARATIVE ANATOMY CHAP. 



Reproduction of Colony-forming Protozoa. 



Freely swimming and stationary attached colonies alike come into 

 existence by incomplete fission and gemmation. Among the colonial 

 Radiolaria (the Polycyttaria among the Spumellaria) separate colonies 

 can mingle with each other ; colonies also can multiply by fission. 



The ordinary method of reproduction of colonial Flagellata and 

 Radiolaria is the production of swarm spores furnished with flagella, 

 which takes place by simultaneous, or more often by successive, division 

 of the body into numerous portions. 



In the Radiolaria, the contents of the central capsule alone take 

 part in the formation of spores ; and this process is preceded by the 

 early or later division of the originally simple nucleus. In the case 

 of Radiolaria which do not form colonies, every spore becomes 

 a Radiolarian. In the colonial species, however, two sorts of spores 

 are developed alternately (1) isospores, representing the usual 

 Radiolarian spores, and (2) anisospores, of which again there are two 

 kinds, smaller mierospores and larger maerospores. The isospores 

 develop direct into young Radiolaria ; the anisospores most probably 

 do so only after the copulation of a micro- and a macro-spore. The 

 young Radiolarian, by repeated fission and gemmation (formation of 

 so called extracapsular bodies), produces a colony. The macro- and 

 micro-spores are either formed in one and the same individual, or in 

 different individuals of the colony. We have here in all probability 

 a regular alternation of generations, one of which reproduces by means 

 of isospores, the other by copulating anisospores. 



The reproduction of the colony-forming Flagellata is particularly 

 important and interesting. In the simplest cases every individual 

 of the colony falls by successive fission into a certain number 

 of portions which sever themselves from the mother - colony, 

 forming daughter -colonies. In other cases (Pand&rina), after a 

 number of generations reproducing themselves as above, a generation 

 arises whose individuals also divide; but the resulting portions 

 (gametes) do not remain united, they separate. These gametes 

 copulate in pairs, the individuals of each pair often differing in size. 

 The product of copulation (zygote), after a resting stage of some 

 duration, again produces a colony by continuous incomplete fission. 

 The reproduction of the Eudorina is distinguished from that of the 

 Pandorina by the formation of two sharply contrasted sorts of gametes, 

 male and female. The sexual generation which produces gametes, 

 and which follows a series of generations reproducing in the usual 

 asexual manner, is either male or female. In the female colony there 

 are certain individuals (ovoid gametes) distinguished by unusual 

 size; in the male the individuals divide into groups (plates) of 32-64 

 spermoid gametes, each of which has two flagella. The plates sever 

 themselves and swim about freely. If such a structure comes in 



