96 M. L. Plate on Ectoparasitic Rotatoria 



need of no further division. I have never seen in our animal 

 fsecal matter of any kind. 



The /e?w«/e sexual organs are situated, unlike those of all 

 other Rotatoria, dorsally with regard to the stomach. They 

 are two elongated sacs (fig. 1, oy), which, in adult animals, 

 traverse the whole trunk, and open, about the level of the 

 hinder extremity of the stomach, into a common efferent duct 

 (fig. 1, du), which opens somewhat further back {a) . This last 

 point strikes one very easily as a transverse slit in examining 

 the dorsal surface of the animal. When the sexual organs 

 have grown to a certain size, they very frequently extend 

 upon the sides of the body to the right and left of the stomach, 

 and in rare cases I have seen an ovary, or both of them, by 

 displacement, occupy the position characteristic of the other 

 Rotatoria, ventral to the stomach. 



Although the structure of the female sexual apparatus 

 appears to be rather simple, I have not been able to arrive 

 at perfect certainty about all its characters, which may be 

 due to the fact that it is subject to different alterations, 

 according to the maturity of the ova. In the condition 

 which I have most frequently met with, a considerable num- 

 ber of ova are arranged behind one another and irregu- 

 larly side by side to form a sac-like organ, and each of them 

 is provided with a nucleus, which is distinguished by the 

 possession of a very large nucleolus. The size of the ova by 

 no means increases from before backwards, but large and 

 small ova follow one another indiscriminately. At the anterior 

 extremity of the whole organ there is, however, frequently a 

 special aggregation of smaller ova, which are distinguished 

 from the others by a much clearer vitellus, i. e. containing 

 fewer fat-granules. We shall probably not be far wrong in 

 ascribing these clearer ova to an early stage of development. 

 All the ova of an ovarium are separated from each other by a 

 distinct wall, and even on very careful examination show 

 nothing in the shape of a membrane enveloping the whole ovary 

 and continued into the efferent duct (fig. 1, du) ; neverthe- 

 less something of the kind must probably be present, and only 

 escape observation by the fact of its clinging very closely to 

 the ova, for how else should these ova, which are not firmly at- 

 tached to each other, but change their relative positions and are 

 frequently separated by gaps, be united into a special organ ? 

 A somewhat different picture from that just described 

 is presented by some individuals, in wdiich the anterior 

 parts of the right and left ovaries of the same female differ 

 considerably. The apex of the left organ may be formed by 

 a rounded body filled with a homogeneous mass of plasma, 



