190 FRANK M SURFACE. 



of reacting, not found or at least not so well marked, in the free 

 swimming balls. When the colony is stimulated as by a slight 

 jar to the dish or a disturbance in the water the whole colony 

 contracts at once and if the stimulus is strong they may remain 

 contracted for some time. This is the usual method of reacting 

 to mechanical, chemical or electrical stimulation. 



After the young animals have once formed a permanent colony 

 they become incapable of repeating the colony formation. If 

 some of the individuals of a permanent colony are removed from 

 the stem they do not behave as they did previous to the forma- 

 tion of the colony. They swim about by means of the ciliary 

 currents, but in an entirely aimless fashion. They neither attach 

 themselves to the old colony nor form a separate colony. I have 

 kept such removed individuals alive for several days but during 

 this time they made no attempt to reform a colony. 



There are likewise several structural changes which take place 

 after the formation of the permanent colony. The animals soon 

 show considerable increase in size, the trochal disc becomes 

 broader and the notch on the ventral side of this makes its 

 appearance. The small circlet of cilia at the foot of the animal 

 disappears and the character of the cement secreted by the foot- 

 gland changes. This cement is no longer dissolved by alcohol 

 as it was in the young specimens. The gland is always much 

 smaller in the adult than in the free swimming individual. But 

 the most striking change and one which perhaps accounts for 

 some of the changes in behavior, is the degeneration of the eye 

 spots. As stated before, the rotifers when hatched possess two 

 red eye spots ; the reaction to light of the swimming ball is 

 probably due to these structures. After the permanent colony 

 has been formed for several hours one finds that the eye spots 

 have disappeared from their previous position while two small 

 red bodies are floating about in the body cavity. In most cases 

 these bodies are inclosed in floating corpuscles which have con- 

 siderable resemblance to leucocytes. Montgomery ('03) men- 

 tions the presence of certain non-cellular corpuscles floating in 

 the body cavities of certain Flosculariidse. He regards these as 

 waste products. Since in Megalotrocha these bodies often 

 enclose the degenerating eye spots and these latter are seen to 



