210 DISCOVERT OF ALPnEUS EDWABDSIT 



merit. Through the centre of every digitatiou runs a tendinous 

 cord terminated by a hook. Within the circu.mference of the disc 

 are found two recurved hooks placed back to back, and connected 

 together by a ring, by whicli and their bases they are firmly held 

 in situ. AVhen the base is cupped, these hooks are erected. A 

 little distance below the bifurcation of the cephalic end, on the 

 ventral surface, may be seen a somewhat spherical cavity, and below 

 this, again, an oval cavity or space, larger and more diaphanous than 

 tlie former. The one has a radiate arrangement, and appears to 

 be connected with the mouth of the animal ; the other is the germ- 

 sac, and contains the next generation. Oftentimes two young 

 ones can be seen within the body of the parent, which they closely 

 resemble in form. While observing these animals with my friend 

 Dr. Bowerbank, we saw the young creature free itself by tearing 

 through the parental envelope, and containing within itself the 

 progeny of a third generation. In some few the oval space simply 

 contained a number of vesicular corpuscles. I was not aware 

 that this parasite had been described until I received a note from 

 my friend Mr. Busk, stating that " it was the Gyrodactylus elegans 

 of Nordmann, afterwards more completely described by Siebold, 

 who was the first to notice that it represents a ' nursing form of 

 animal,' and, as suggested by Siebold, is only a transitional, 

 asexual form of a Trematode, such as Polystomuvi or Octobotliriiim ; 

 that it was origmally found by Nordmann on the gills of the 

 Carp, but that Siebold mentions its occurrence on the fins of two 

 species of Sticklebacks." 



Siebold notices two species of Gyrodactylus — G. elegans and G. 

 auriculatus, — to which Dujardin has added a third, G. anchoratus. 

 As this parasite has not, so far as I know, been before noticed as 

 occurring in this country, and is in many respects a very interest- 

 ing object, and as it may be obtained plentifully at the present 

 time, I have ventured to give the above brief description of it*. 



Discovery of Alplieus Edwardsii on the Coast of Cornwall. 



By Jonathan Couch, F.L.S., &c. 



[Read April 5th, I860.] 



The only species of the Crustacean genus ^Z^/^ezf* hitherto known 



in the waters of the British Islands is the A. ruber ; and this is 



* [Mr. Bradley has since noticed in the interior of some of the fishes infested 

 ■with the Gyrodactylus, some minute Trematode Wonns, which may probably 

 have some genetic connexion with it. — G. B.] 



