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THE POPULAR SCIENCE MONTHLY 



Hwm mama — ------ *". / - 



One of tee Happy Families in the Aquarium. 



erated. The semi-transparent squids, with posterior triangular fins, 

 swim back and forth as delicately poised as submarine monoplanes. 

 When a live fish is placed in the water the squid darts at it, grasps it 

 firmly with the suckers or the tentacles and cuts off the head, eating 

 only the body. The cuttlefish, with broader body, striped like a zebra, 

 and big elephantine head, constantly undulates a fin-like fringe around 

 the border of its mantle, as it nervously drifts here and there. Fre- 

 quently it wriggles into the sand which it throws upon its back, or, 

 if much disturbed, ejects a cloud of ink in which it disappears. The 

 large octopus has a body that suggests both a toad and a spider, with 

 highly developed eyes and brain projecting above it. Generally this 

 devil-fish lies sleeping in a corner of the rocks, or lazily reaching out 

 and creeping about by means of eight long tentacles that express a 

 giant's strength. With a spurt of water from its siphon the octopus 

 may dart rapidly through the tank, and by directing the tube of its 

 siphon, go whither it wills. Lying upon the bottom of an open trough, 

 often buried in the sand, is the very interesting electric ray. If one 

 presses the fingers upon the broad body where it runs into the tail he 

 will, in the words of a Cook's guide, " get a strike." The electric tis- 

 sues are descended from muscle fibers which in the course of evolution 

 have come to produce electricity instead of motion. In the embryo 

 ray the primitive muscle cells first appear, then they swell out anteriorly 

 and shrivel up posteriorly until each loses the characteristic striated 

 muscle structure and becomes an electric plate lying in a little com- 

 partment embedded in a jelly-like substance. Electricity is produced 

 by some chemical action upon innumerable minute granules stored up 

 in the protoplasmic network pervading the electric plates. The shock 



