the excretory system consists of but two flame cells and 

 two capillaries. 



A few rainut^e -tft'*r figure 15 had been drawn, I "ms 

 fortunate enough to observe the miraciciium escaping from 

 the egg* After many and vigorous lunges the operculum 

 opened a a if nn a hinge (fig 17). Within three seconds 

 the whole rairacidiura was out and swimming vigorously 

 about in search of its proper host. The operculum 

 measures 0.023 mm. in diameter. Inside the newly hatched 

 egg (fig* 17) is to be seen a considerable amount of 

 waste and oily material. This m to rial as well as the 

 oporouluia is lost, however, inside of a few hnurs (fi^s. 18 

 and 18a). 



Altho the ech ino 9 tome eggs are much alike in shape they 

 differ oonBidernbly in eias*. Uven in the same species there 

 is considerable variation. Perhaps the largest eohinostoine 

 egg of unquestionable record is thrrt of P eao 80 *aurn s a^i na t urn 

 (Hatz), the length of Thioh is 0.130 ram. and the/*ridth C.089 

 mm. t but even here there is great variation in size. On 

 of the smallest eohinostoae e;$g produced is by Mo nil if er 

 3pinulp_sus. (Hud), measurin but 0.069 to 0.072 mm. in length 

 by 0.048 to 0,050 rara. in width. Alttou^h variation in size 



of eggs is common to nearly all di genetic tremmtcdes, yet 



\ 



no speoies S'vuas to have greater variation than the records 

 given for ^ohinostoanL revolutma* The ^r-?atest length yt 

 recorded for this species is by LOO-^B (1899, p. 682), w?io 

 has gotten theextrffnw measurement of 0,134 mm. Throughout 

 the whole genus Bchino sterna, however, the mean is not 

 far from 0.110 mm. the gre.it variation in size of eggs in 



