92 American Quarterly Microscopical Journal. 



segmentation carefully studied. The ova vary in size, but 

 are quite uniformly oval in shape. At the right of Fig. i are 

 some of these ova magnified looo diameters and reduced. One is 

 undergoing segmentation (Fig. i, "). This will keep contracting 

 and expanding rapidly, each contraction making the center nar- 

 rower and narrower, until separated completely into two parts, 

 each part whirling about at a terrible rate. The embryo (') 

 has just left its covering (*), an appearance obtained by press- 

 ing gently on the cover-glass, causing the rupture seen here 

 and the escape of the embryo. The embryo at ' was from 

 the distome at its left, and in shape is not unlike a jug. It is 

 covered completely with ciliated epithelium. These cilia are 

 very active, and, as a result, the body revolves on its axis 

 at a high rate of speed. Their motion is so rapid that with 

 high powers it is exceedingly difficult to keep them in the 

 field. Evidently they have no idea where they are going, for 

 they will strike some obstruction with force sufficient to give 

 them a considerable rebound, when for a moment they will 

 remain perfectly quiet, only again the next moment to go 

 whirling about. Examined closely we see the commencement 

 of a cephalic sucker. 



After a time this embryo develops in its interior another 

 organism, a sporocyst (Fig. 4, upper figure, after Cobbold). 

 At first the appearance of this sporocyst is very simple, hav- 

 ing a faint semblance of a head, body, and a short, straight 

 tube for a digestive canal. The figure represents the sporo- 

 cyst in an advanced condition. There is a well-developed head 

 and body, with a very prominent tail {c). We see an oral 

 sucker in front (/), communicating with the bulb of the oesoph- 

 agus (/), which passes directly into the blind digestive tube, 

 or stomach {g), which contains here particles of food (//). At 

 b and / are irregular bodies which will develop into organisms 

 called cercariae. After their more complete development and 

 escape from the sporocyst, we have the appearance given 

 in Fig. 4 (lower figure). Here we have no difficulty in 

 recognizing the several parts. The cephalic sucker {a) is plain- 

 ly seen with the pharynx {li) communicating with the oesoph- 

 agus [c). The digestive tubes or stomachs {0) are seen, also the 

 posterior sucker, or acetabulum {e). The water-vascular and 

 excretory system (^/and/) are here shown. The tail (//) is 

 prominent, and has a marginal fringe (/). 



