1920] joh iison : Life < 'ycle of Ecliiiiostoma Revolutum (Froelich) 367 



.270 mm. This points to the fact that the ventral sucker in the adult 

 plays a very important function in attachment. 



The distance betwen the oral and ventral suckers in the adult is 

 about 1.05 mm., whereas in the cercaria it is about 0.023 mm. This is 

 a gain of less than four and a half times. Since the body of the 

 cercaria is about 0.5 mm. in length, and the body of the adult is about 

 9 mm. or eighteen times larger, it is evident that the greatest, region 

 of growth of the adult body is posterior to the ventral sucker. 



The bladder of the excretory system of the adult is interesting in 

 that the muscular sac (lb in the cercaria) measures more than one- 

 fourth of the total length of the worm, whereas in the cercaria it is 

 less than one-tenth of the length of the body. The muscular tubes 

 (lc in the cercaria) are also much elongated, measuring nearly three- 

 fifths of the total length of the body of the adult, whereas in the 

 cercaria they measure but one-third of the body length. The con- 

 cretions in the tubes of the cercaria 's bladder (Id in the cercaria) 

 are not to be found in the adult, although the tubes are about as great 

 in diameter as in the cercaria. The ascending tubes of the bladder 

 (le in the cercaria) are long in the adult as in the cercaria, extending 

 nearly the whole length of the body. Several other collecting tubules 

 and accessory collecting tubules were also seen (fig. 49). The muscular 

 sac division of the bladder was found to branch to either side a number 

 of times, these branches in turn breaking up into smaller and smaller 

 tubules that exend almost all over the body. Flame cells were never 

 seen but the cilia in the main collecting tubule were very evident, 

 being arranged in bunches and thus appearing much like large flame 

 cells. 



So far as the excretory system in the adult can be traced it is much 

 like that of the cercaria. However, each part has been modified in 

 length and size to meet its place in the adult ; and the bladder is very 

 much branched. If the flame cells, capillaries, accessory collecting 

 tubules and collecting tubules could be accurately traced in the adult 

 I should judge that they would be the same in number and similar in 

 pattern. The great increase in the size of the adult over the cercaria 

 would have to be met, so far as draining the wastes from the body is 

 concerned, by the fine tubules of the branches of the muscular sac of 

 the bladder. 



As stated previously, Looss (1899), Liihe (1909), and others have 

 undoubtedly placed two species, perhaps more, under the name 

 Echinostoma revolutum (= Distomum eehinatum Zeder). 



