^ OBSERVATIONS OX FRESH-WATER POLYZOA. 131 



The statoblast at the earliest stage of its (levelopniont is of 

 a milky- white color. The chitinoiis parts as they form tliemselves at 

 first present hght 3'ellow color, which, as the development advances, 

 darkens to the characteristic hue of the mature stato1)last. 



On attaining a certain size, the statoblast bulges out the fimicidnr 

 wall chiefly on one side, with its plane always parallel to tlie axis of 

 the funicidas. When many statoblasts develope in the same fanicuhis, 

 tliey generally lie alternately disposed, by wliich means econoni}- of 

 space is effected. It is on that side of the statoblast with whicli it 

 joins the funicular tube that the cystogenous cup closes. 



The number of statoblasts that develope in a single polyzooid is 

 usually five or six, in some cases as much as eight. Of these, the 

 uppermost one is the oldest and the lowest the latest formed, so tliat 

 at a certain period statoblasts in various stages of development in 

 serial order may be seen in the same funiculus. In those old poly- 

 pides that occupy the central part of a colony all the statoblasts usu- 

 ally attain maturity, while in the peripherally situated younger poly- 

 pides the latest formed statoblast is generally still in c|uite an early 

 stage of development at the time when the colony begins to dissolve 

 away. These immature statoblasts undoubtedly suffer common decom- 

 position with the mother-colony. As every polyzooid produces 

 statoblasts, their number in the entire colony is really very great. 

 Once I counted no less than 870 statoblasts in a very small colony 

 of about 1.5 cm. in diameter. 



