FORMATION OF NEW COLONIES OF MEGALOTROCHA. 185 



in stretching the thread holding it fast, so that later it comes to 

 lie outside the limits of the old colony (Fig. i). In the course 

 of time this thread breaks and the young ball swims away. 



From the time the first individuals are hatched until the ball 

 breaks loose there is usually a lapse of three or four hours. 

 Since all the eggs of one brood are not deposited at the same 

 time the period of hatching often extends over several hours. 

 The long time that it takes for the ball to form and break away 

 gives opportunity for the later individuals to hatch and get into 

 the new colony. Often there are a few young that do not get 



P'lG. i. Sketch to show formation of the swimming ball, e, eggs, attached to the 

 adults; r, young animals before coming into the ball (b) ; /, mucilaginous thread 

 holding the ball to the mother colony. 



into the ball before it breaks away. These swim about for a 

 time near the old colony and then may settle down on a near-by 

 stem. Apparently these do not long survive the attacks of their 

 enemies, for later I have seldom been able to find them, and I 

 have never seen an isolated adult. By thus losing a few individ- 

 uals in every generation the colonies would evidently continue to 

 get smaller, for after the ball breaks away no new individuals are 

 added to the colony. Such a decrease in numbers would un- 

 doubtedly take place were it not for the overlapping of the 

 broods. One generation of eggs is laid so soon after the other 

 that, in many cases, a large number of the second brood hatch 

 in time to get into the forming ball. Occasionally, but not often, 



