1880.] 



MICROSCOPICAL JOURNAL. 



231 



ing brightly in the dish. They 

 could be seen escaping from almost 

 all parts of the body ; none, how- 

 ever, were observed coming from 

 the lower part of the foot. After 

 their escape they would swim about 

 for a moment or two in the neigh- 

 borhood of the snail, then move 

 away, usually near the surface of 

 the water, to the sides of the dish. 



In form the body, when con- 

 tracted, was globular, and this form 

 was maintained by the animal while 

 actively swimming about ; occasion- 

 ally it would cease swimming, 

 allow itself to settle upon the bottom 

 of the dish, or some other object, 

 and then extend its body, which 

 then assumed a somewhat triangu- 

 lar form. During the extension of 

 the body the tail invariably became 

 contracted and quiet, — then con- 

 versely the body would contract, 

 becoming again globular, and the 

 tail Would become extended and lash 

 about with great rapidity. 



Fig. 34. — The triangrular form ; the animal has fallen 

 upon some object, as the side of the dish, and its body 

 is undergoing alternate contraction and extension ; 

 it is really preparing to encyst itself. 



When viewed with the naked 

 eye the bodies appeared to be of a 

 light color, but under the micros- 

 cope the color was dark, and it is 

 probable that the cyst of the suc- 

 ceeding stage is darker than the 

 original body of the larva. With 

 an inch objective, the bodies appear- 

 ed to be composed of granular ma- 

 terial — no intestinal cavity visible — 

 two. distinct eye-spots were seen 



near the anterior extremity, and 

 just behind and between these was 

 a third dark, pigment spot, which 

 was not as distinct as the eye-spots. 

 An anterior, suctorial disc or 

 mouth was observed on the under- 

 side, near the anterior extremity of 

 the body, but no additional sucto- 

 rial disc or acetabulum was to be 

 found. 



The tail was semi-transparent — 

 light colored- — and capable of very 

 great expansion and contraction, 

 showing that it possessed great mus- 

 cular power. As it contracted, dis- 

 tinct transverse grooves or furrows 

 were seen, which alternated with 

 others on the opposite side. In 

 general form it was nearly cylin- 

 drical, slightly flattened vertically, 

 larger near its attachment to the 

 body, but grad- 

 ually tapering 

 to the extremi- 

 ty; just poste- 

 rior to the at- 

 tachment to the 

 body it was con- 

 stricted, but be- 

 came slightly 

 enlarged to 

 form a globular 

 head for at- 

 tachment to the 

 animal. 



If allowed to ^ r^^ . ^ ^ 



. -, Fig. 35. — The body as lix- 



remam m tne ed ; the process of encysting 



Ir.-..^^ /^loV. nn having already begun; the 



large aiSn Un- (3^1 Anally disengages itself 



disturbed, they/^^'"^^'"^ about violently.^ 



would retain this form for a consi- 

 derable time — perhaps from fifteen 

 to twenty minutes — but if transfer- 

 red with a few drops of water to the 

 stage of the microscope, they quickly 

 prepared to encyst themselves. This 

 process was indicated by the ani- 

 mal becoming very restless, ra- 

 pidly extending and contracting 

 its body and tail. A little 

 later, the acts of contraction and 

 extension were more prolonged, 



