EXISTIXG ORGANISMS— CLASSIFICATION 



23 



#-gy»i.C. 



Colonial Forms. Such forms are highly developed in the 

 Coelenterata (Fig. 4), among them such species as the Portuguese 

 man-of-war, which hves in free swimming colonies made up of 

 numerous modified individuals which carry on limited activities 

 for the common good. Many of the simpler hydroids display 

 three forms simultaneously, viz., 

 polyps, asexual reproductive in- 

 dividuals and sexual medusoids 

 similar to small jellyfishes, which 

 later detach themseh'cs from 

 the colony. All of these forms 

 are connected structurally, yet 

 in degree their differentiation 

 is not unlike that of the castes 

 of social insects. In the honey 

 bee colony there are three 

 forms, the functional sexes or 

 queen and drones, and the 

 workers, which are imperfectly 

 developed females with certain 

 modifications peculiar to their 

 own caste. Among the ants 

 division of labor is accompanied 

 by the development of distinct 

 forms by the mochfication in 

 various directions of the three 

 fundamental types. That these 

 differences of individuals are 

 closely associated with division 

 of labor in all cases is obvious, 

 and the two are generally sup- 

 posed to have developed to- 



Fio. 8. — Blood fluke, Schistosoma hae- 

 malohium. Male (cf ) carrying female 

 ( 9 ) in ventral groove; int, intestine; 

 gyn. c, ventral groove or gyneco- 

 phoric canal; m, mouth; v. s., ventral 

 sucker, x 8. (Reprinted by permis- 

 sion from Animal Parasites and 

 IhoiKin Disease by Asa C. Chandler, 

 ]:)ublished by John Wiley and Sons, 

 Inc.) 



gether. 



Alternation of Generations. Still another type of polymor- 

 phism is alternation of generations such as that found in many 

 plants and some of the lower animals. In Obelia (Fig. 4), for ex- 

 ample, a member of the phylum Coelenterata, asexual individuals 

 produce the medusoids by budding, while the whole colony is 

 nourished by the polyps. The medusoids swim away from the 

 colony, mature their germ cells, and by this process of sexual repro- 



