6/6 THE POPULAR SCIENCE MONTHLY. 



tain animal forms, belonging to the Molhiscan races, we may discover 

 equally admirable examples of economy in natural work. Among the 

 cephalopods or cuttle-fishes we observe such features. Any one who 

 has seen an octopus resting in its tank in an aquarium must have been 

 struck by the puffing and blowing movements of the sack-like body, 

 the nature of which excited Victor Hugo's imaginative powers in the 

 "Toilers of the Sea." The octopus is seen to inspire and expire with 

 great regularity. The soft body expands and contracts rhythmically 

 enough to excite a natural comparison between its respiratory acts and 

 our own. If we could dye the water so that our eye could follow the 

 currents which the octopus inhales and exhales, we should perceive 

 that at each inspiration the soft body expands, and water is drawn in 

 two currents into the neck-openings. These openings lead directly 

 each into a gill-chamber of the animal. Here, inclosed in its own cav- 

 ity, we find a plume-like gill. In its nature, this structure is simply a 

 mesh-work of blood-vessels, and thus comes to resemble a lung in its 

 essential features. Impure blood that is, blood laden with the waste 

 materials of the octopus-body, with the products of the vital wear and 

 tear is driven into the gill on one side. Subjected to the action of 

 the oxygen gas contained in the water breathed in, the blood is puri- 

 fied. Its waste materials are given forth to the water, and it is passed 

 onward out of the gill on its way to the heart for recirculation through- 

 out the cuttle-fish frame. 



Breathing in oxygen entangled in the water is, therefore, in the 

 case of the cuttle-fish, an analogous act to that seen in higher animals, 

 which inhale oxygen directly from the air. The octopus, however, 

 performs an expiratory act likewise. Placed below the head is a short 

 tube, named in zoological parlance the " funnel." When cuttle-fish in- 

 spiration has come to an end, expiration begins. The body contracts, 

 and the water, which a moment before was drawn into the gill-cham- 

 bers by the neck-openings, is expelled from the "funnel." The open- 

 ings of entrance are guarded by valves. These close when expiration 

 begins, and the water has no choice save to find a forcible exit by the 

 tube just named. So far, in octopus existence it would seem as though 

 there was no economy of power exhibited in the act of breathing. Mus- 

 cular action expands the soft body, and muscular force contracts it. 

 There is exhibited here a plain difference between the octopus and the 

 higher vertebrate. 



But the story of cuttle-fish economy is not yet completed. A 

 moment more and your octopus, which sat crouched in the bottom of 

 the tank, is seen to wing its way through the water. It skims like a 

 living rocket through the clear medium in which it lives, as if impelled 

 by some marvelous and invisible agency. The secret of this flight is 

 the solution of cuttle-fish economy and reserve force. So long as the 

 resting-mood prevails, the water used in breathing is ejected slowly, 

 or at least without any marked display of force. But when locomo- 



