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seated below the ovary. A pair of longitudinal muscles pass from 

 the head to the extremity of the body, one on each side ; and one 

 from each side of the gizzard to the same part : there are also seen 

 three or four transversal muscles. (These are all shown at d). The 

 head, which is broad and prominent, is surrounded by a wreath of 

 cilia, and a large claviform process projects over the occiput or 

 stands erect. This process, so commonly found in the Rotifera, is 

 considered by Prof. Ehrenberg as a respiratory tube ; but I have 

 reason to think it is the first rudiment of the antennae of the higher 

 classes of annulose animals, in which great division I am sure the 

 Rotifera find their place. When the head is withdrawn by the con- 

 traction of its special longitudinal muscles, the surrounding margin 

 is drawn into puckers. The whole animal is colourless, with the 

 exception of the eye : but the stomach is generally filled with green 

 food ; and the opaque developing egg frequently imparts a dark hue 

 to the abdomen, viewed by transmitted light. 



The habits of this inconspicuous little Notommata are curious, for 

 it is parasitic in the elegant Volvox globator ; hence Ehrenberg gives 

 it the appropriate designation of " The Pirate." On examining seve- 

 ral Volvoces, even with a pocket lens, we may frequently detect such 

 as are thus tenanted, by their containing one or more spots differing 

 from the young clusters in form and colour. Each of these spots is 

 found to be a Notommata, snugly ensconced within the globe, in 

 the spacious area of which it lives at ease, and swims to and fro, 

 like a gold-fish in a glass vase. We see it for the most part, how- 

 ever, clinging to the inner surface of the circumference, engaged in 

 devouring the green monads with which its gelatinous expanse is 

 studded, or else eating away the embryo clusters. Fig. a repre- 

 sents a portion of a Volvox, ^ of an inch in diameter, viewed with a 

 power of 220 linear ; and b is one of the embryo clusters, partially 

 devoured. The action of the protruded jaws of the Notommata, as 

 it eagerly nibbles away at the monads, is very energetic ; but its 

 progress is not commensurate with its vehemence. J have not been 

 able to see one actually detached and swallowed. Frequently two or 

 more NotommaUe are found in the same Volvox, and I have seen as 

 many as four, with an egg besides. They do not interfere with each 

 other, but each pursues his own avocation. 



It is chiefly the smaller Volvoces that contain the parasite, espe- 

 cially those which have the embryos very immature. I have not 

 seen any loose in a large Volvox, but in embryos almost grown, and 

 nearly ready for escape, I have several times seen a Notommata. If 



