A PUZZLE TO ZOOLOGISTS. 251 



Annelida ; 3. Tlie Lernasan Crustacea ; 4. The Ai'ach- 

 nida." * 



Place it where we will, the animal is very interesting, 

 either when darting about in a glass vase, flapping the water 

 with its tail, and fixing itself to the side of the glass (using 

 the vent as a sucker?), or seen on the microscope stage, 

 where its extraordinary transparency obliges a liberal use of 

 " stops." It is then seen to have a head with a formidable 

 set of hooks (which, however, do not seem to fulfil the office 

 of jaws), and two large eyes. The narrow body is divided 

 into two equal lengths (in my specimens this was so ; in the 

 figures published by Mr Busk and Mr Gosse the anterior 

 portion is considerably the larger) ; in the upper half lies the 

 straight alimentary canal, terminating in a cUiated orifice ; 

 on either side of the canal lie the ova ; in the lower half, 

 which is longitudinally divided by a septum, the whole cavi- 

 ties are filled with granules of various sizes, moving, by a 

 scarcely perceptible progress, round and round, like food in 

 the stomach ; and these granules prove to be the spermatozoa 

 which issue from the two orifices near the caudal expansion. 

 It is about the quarter of an inch in length, and difiers in 

 several points from the species described and figured by Mr 

 Gosse in his Tenby and Handbook, and by Mr Busk in the 

 Microscopical Journal.f For instance, it has no anterior 

 fins ; and the posterior fins, which arise near the oviducts, 



* Report of British Association, 1851. Sections, p. 78. 

 t October 1855. In this paper the reader will find a summary of all that 

 ■was then known on the subject. 



