Um- 



bo that in one larval Treraatode at least, 

 the annulated structure of the body exists, 

 as well as in the larval Planaria. 



Returning now to Steenstrup's narrative, 

 he tells us that these "Echinate Cercaria! 

 (Fig. 164, A, parent nurse; e, germs; 

 a, nurse; B, larva), are found by thous- 

 ands, and frequently by millions in the 

 water, in which two of our largest fresh- 



stagnalis, have been kept." After swim- 

 ming about in the water some time they 



such numbers tha 



« (B, •) to tb 

 latter look i 



,vt're-l 



of the ! 

 with bits 



The Cercaria by contracting its body and violent lashing of the 

 tail forces its way into the body of its host, loses its tail, and then 

 resembles a mature Distoma. By turning about in its place and 

 secreting a mucus, a cyst is gradually formed, with a spherical 

 shell. This constitutes the "pupa" state of the Cercaria, first 



