260 LEPTODORA HYALINA. 



Btructure, formed in several lobes externally, but not having any divisions 

 internally. It has a regular pulsation of about 150 beats per minute, 

 each contraction appearing to flow upwards as a wave upon the surface of 

 the vessel. The heart has an aperture at each end, but no circulating 

 vessels have been traced from it, nor in any other portion of the body. 

 Although, however, there is not any system of circulating vessels, the 

 circulating particles do not travel promiscuously through the body, but 

 appear to flow in tolerably definite channels in the different parts of the 

 body, in which they can be observed. 



The ovaries occupy a great length of the abdomen, extending from 

 near the under side of the mouth to the commencement of the stomach, 

 as shown in Fig. 2. There are two ovaries, one occupying the upper and 

 the other the lower half of that space, and meeting in the centre, where 

 the external openings of the oviducts are situated, at the third segment 

 of the abdomen from the tail end, and corresponding with their position 

 in Daphnia. The eggs are laid in the incubating chamber, formed by the 

 enclosing carapace, (as shown in Fig. 3,) and have the appearance of being 

 secured by means of some adhesive material to the inner wall of that 

 chamber. In a living specimen that I frequently examined under the 

 microscope during several successive days, although the rapid movements 

 of the animal caused the tail end of the abdomen to be violently jerked 

 in and out of the front of this chamber, there was not any motion per- 

 ceptible in the eggs within the chamber, which remained quite stationary 

 in their original position, appearing to be attached in their places within 

 the chamber. In Daphnia the eggs remain loose and freely floating in the 

 corresponding space of the incubating chamber, but they are prevented 

 from escaping by the tail end of the animal blocking up the open 

 bottom of the chamber, until the time when the hatched young are 

 matured, and these are then allowed to escape by the tail being jerked 

 forward, leaving the chamber open at the bottom. In one mounted 

 specimen (drawn in Fig. 3) that was lent to me by a friend, there were 

 originally seven eggs in the chamber, but four of these have subsequently 

 become detached, and are now floating freely about the cell in which the 

 specimen is mounted, three eggs alone remaining fixed in the chamber ; 

 and in this instance it may be supposed that the action of the mounting 

 fluid in the cell has gradually loosened the attachment of the eggs by 

 softening the adhesive material that held them in their places. 



Leptodora, though only now discovered in this countz'y, has been 

 known for twenty years on the Continent. It was first discovered in 

 1858, in a moat round Bremen, by a chemist namedKindt and Dr. Focke ; 

 then in 1867 it was found both in Denmark and Norway ; and in 1868 in 

 a lake near Kasan in Russia, in Lakes Constance and Geneva in 

 Switzerland, and in Lago Maggiore in Italy. There seems to have been 

 now an interval of eleven years without any record of Leptodora being 

 found elsewhere,* until the discovery of it in this country in the present 

 year by the Birmingham Natural History and Microscopical Society. 



* Since the above paper was read, the discovery of Leptodora in twenty-one 

 different lakes of Italy has been announced by Professor Pavesi, of Pavia. 



