206 THE AMERICAN MONTHLY [November, 



Biological Notes. 



By L. W. CHANEY, 



NOKTHFIELD, MINN. 



Trematodes. — The writer has, for some years, as he was able, been giv- 

 ing attention to tlie embryology of the fresh-water mussels. During one stage 

 of their life-histoiy the embryos of these mussels live in broods pouched upon 

 the sides of fishes. In searching for these pouches, occasion has been taken to 

 dissect some of the fishes, and in them have been found encysted forms which 

 seem to be one generation of Trematodes. If this should prove true, pre- 

 ceding stages should be found in our snails. 



A brief sketch of the life-history of some of the Trematodes may suggest 

 lines of investigation which the worker with the microscope and scalpel might 

 undertake with interest and profit. The small eggs passing from the host 

 with the excretions, and falling in some damp place, go through the usual 

 segmentation, and become ciliated embryos having some features of the adult 

 worm. These embryos, boring into the tissues of the snail, assume a state 

 called a Sporocyst when without mouth and alimentary canal ; in other species 

 a Redia, with mouth and alimentary canal. Within the Sporocyst, or Redia, 

 there arise a number of oval larv£e having a muscular tail of consider- 

 able length. These larv^ burrow out of the cyst and from the body of the 

 snail. Swimming about, by means of the strong tail, they find a new host, 

 frequently a fish. Into the tissues of the fish the larva called a Cercaria forces 

 its way, and there becoming encysted, assumes the form of the adult except 

 that the generative organs are not developed. The fish being eaten by some 

 other animal, the larva set free undergoes a final metamorphosis, and assumes 

 the adult and sexually mature state. It thus appears that in three different 

 animals may be found three stages of the same worm. Of these three stages 

 the writer has casually met with one. He would be very glad of hints from 

 any source which would throw light upon the matter. 



Tape-worms. — In a letter. Prof. C. W. Hargitt, of Miami University, men- 

 tioned finding a number of tape-worms in the small intestine of the cat. In 

 such literature as is at hand, no mention is made of this as a common occur- 

 rence. One species is named as so occurring with its larval state in the field- 

 mouse. As, at the time, a number of cats were under examination in our 

 laboratory, they were dissected with a view to noting their condition in this 

 respect. Curiously, the only one of the animals affected was one in the habit 

 of hunting in the fields. Those cats whose habits were strictly domestic, in 

 no case coming under observation, showed the parasites. The range of ob- 

 servation is, of course, too limited to form a basis for any conclusion. 



Hair-worms. — Very recentlv, speaking of the occurrence of the Gordius, 

 or Hair-worm, in our streams, there appeared an explanation of the wide- 

 spread belief in the myth that hairs from the tails of horses are transformed 

 into such worms. The experiments suggested may lead to some very curious 

 conclusions concerning the physics of hairs. Microscopic examination of 

 cross-sections of horsehairs may reveal what are the peculiarities of the cortex 

 which cause unequal changes when moistened and thus produce writhing mo- 

 tions so similar to the muscular movements of Gordius. So deceptive are 

 these mechanical movements of the hairs that one can readily pardon the be- 

 lief that they are really ti-ansformed. Will not the microscopists follow up 

 some lines of inquiry herein suggested ? 



Carleton College, Oct. lo, /888. 



