1861.] DR. W. BAIRD ON LERNiEA CYCLOPTERINA. 239 



loosely curled round some shells of a Purpura that were attached to 

 the surface of the glass of the tank. 



This is an approach to the prehensile tail of the Hippocampi, but 

 still very different from the habit of that genus. 



Mr. Bartlett informs me that, whatever may be the colour of some 

 of the fishes, such as Flounders, Plaice, Soles, and Thorubacks, when 

 placed in the tank, they soon modify their colours so as to be very 

 like that of the shell or sand which forms the ground of the tank ; 

 and as shells and shell-sand are now generally used to make the ground 

 of the tank, the fisii become of a pale-brown, more or less mottled 

 colour. 



The flat fish, as Flounders, Plaice, and Soles, lie tranquilly at the 

 bottom of the tank, on the sand, with their eyes prominent, and their 

 mouth usually rather exserted and partly open ; but they swim with 

 facility, bending the side (or, rather, what in other^fishes we should 

 call the dorsal and ventral edges) .down, so as to raise the central line 

 of the body, and propel tbeniselves with their tails. The pectoral 

 fins seem to be but little used, and they are often very rudimentary ; 

 the ventral fins, which are also small when present, are usually ex- 

 panded when the fish lies on the sand. 



It is much to be regretted that persons who have the leisure and 

 opportunity of observing these and other fishes in tanks, do not give 

 us more particulars of their manners, and especially of the means by 

 wliich they propel themselves through the water, which is evidently 

 very different in the various families and genera. The elongate, cylin- 

 drical or subcom pressed, or many-angled Syngnathus is generally 

 straight and stiff while moving from place to place ; while the elon- , 



gated, rather compressed Blennies, as Guiitellus and Zoarces, pro- "Y^ / 

 pel themselves forward with a horizontal, serpentine motion, appa- 

 rently keeping their bodies erect by the dorsal fin and the expanded 

 pectorals. 



There is one circumstance connected with the fishes in these tanks 

 which I have never been able to understand ; that is their apparent 

 blindness to any external object that is presented to them from the 

 outside of the tank, when it is offered to them on a level with their 

 eyes or apparent range of vision. I have attempted to disturb them 

 with my hand, with a red handkerchief, and wilh many other bodies; 

 but I have never observed them show the slightest idea of there 

 being any danger, or even take the slightest notice of the approach- 

 ing body ; yet they are easily disturbed if the object is so presented 

 to them as to appear to descend towards them. 



3. Note on the Lernjea cyclopterina occurring in the 

 Gills of the Cyclopterinus spinosus, a Fish from 

 Greenland. By W. Baird, M.D., F.L.S., etc. 



In the 'Fauna Groenlandica,' O. Fabricius shortly describes a 

 species of ierwtEa as occurring in the Cyclopterinus sjyiiiosus. Kroyer 

 in his ' Tidskrift ' figures the same parasite ; but his figure varies so 



