56 BOAED OF AGRICULTUEE. 



Many observers state that these worms have no mouth and 

 no digestive organs whatever, but obtain their nutriment by 

 absorbing the nutritive materials by which they are surrounded 

 in the intestine of their host directly into their own tissues, 

 after the manner of the tape-worms. M. Lespes* states, how- 

 ever, that Echinorhynchus davceceps, found in the minnow, etc., 

 has a complete alimentary system. The mouth is very small, in 

 form of a pore, opening at the end of the proboscis and raised 

 upon a small mobile papilla. This mouth communicates with 

 a short digestive cavity, in the form of a blind sac. He states 

 that he has seen the refuse of the food ejected from the mouth. 



Upwards of 100 species of these worms have been described, 

 nearly all of which are referred to the genus Echinorliynehvs. 

 ■ They are especially abundant in birds and fishes. 



Those species in which the development has been studied, 

 have a kind of alternate generation, the young embryo be- 

 ing very different from the parent, and afterward developing 

 in its interior another form, which in turn becomes like the 

 grandparent. M. Lespes states that EJ. clavwceps produces 

 " cocoons " containing 150 to 200 eggs. The embryos devel- 

 oped in the eggs are capable of moving while still in the shell, 

 and remain alive for a year. On feeding a snail with food 

 containing these eggs, they hatched in his intestine, and the 

 free embryos were quite lively and active, and furnished with 

 two pairs of hooks for boring purposes. They had consider- 

 able resemblance to the free embryos of tape-worms and no 

 doubt have similar habits, but they failed to undergo their 

 transformations in the snail. 



Leuckart fed the eggs of E. proteus, found in the trout and 

 other fishes, to a small crustacean, Gammarus pulex. The eggs 

 hatched in a few days and the young embryos bored their way 

 through the intestine into the general cavity of the body, some 

 of them penetrating into the limbs. In the course of three 

 weeks they grew larger and the granular mass still in the inte- 

 rior of the body of these embryos developed into a distinct or- 

 ganism, which afterwards developed a proboscis, muscles, and 

 the other peculiar organs of an Echino7'hynchus,hecom.mggmd\i- 



*Journal cle 1' Anatomic, 1864, p. 683 ; Gunthcr's Zoological Record, 1865, p. 747. 



