til THREE CRUISES OF TIIK u BLAKE." 



by the Fish Commission off Martha's Vineyard from a depth 

 of over 1,000 fathoms. 



The giant squids (Fig 1 . 281) of the North Atlantic (Architeu- 

 this), occasionally thrown up on the shores of Newfoundland, 

 attain an immense size, the arms measuring fully forty feet in 

 length. They probably live in the regions where food is most 

 abundant, upon the slopes, near the boundary of the continen- 

 tal plateau. It will be some time before we are able, with our 

 present appliances, to capture such monsters from the depths at 

 which they live. The Belemnites, so characteristic of some of 

 the tertiary deposits, have not as yet been dredged. 



GASTEROPODS AND LAMELLIBRANCHS. 1 



The Mollusca obtained by the " Blake " are notable in several 

 respects. We may refer to the absence or rarity of very minute 

 forms, which are only accidentally preserved in the contents of a 

 trawl net, even from comparatively shallow water. It is hardly 

 to be expected that, in the long washing which the contents of 

 a trawl undergo while hauled in from deep water, anything small 

 enough to go through the finest meshes of the bottom net 

 should be retained. Yet large shells appear to be rare in the 

 great depths, and are usually so fragile that their destruction or 

 fracture is almost inevitable. Deep-sea dredging has thus af- 

 forded few specimens of even moderately large size, judged by 

 the standard of shallow-water or littoral shells. Among naked 

 mollusks several species of unusual size have been found by dif- 

 ferent expeditions. One as large as an orange, discovered by 

 the " Challenger," was named by Dr. Bergh Bathydoris abys- 

 sorum. It is perhaps the largest nudibranch known ; it has a 

 transparent and gelatinous consistency, and with neither eyes 

 nor otocysts it must have led a remarkably sluggish existence, 

 blind and deaf as it was. 



Abyssal mollusks are probably less active and energetic than 

 their congeners of the shores. This is indicated by the loose- 

 ness of the tissues, less favorable to prompt and violent action 

 than a more compact muscular system would be. The tena- 



1 Mr. Dall has kindly prepared for me mellibranchs, and supervised the drawing 

 the account of the Gasteropods and La- of the figures. 



