204 THE OCEAN WORLD. 



recorded his observations on some of these animals of smallest dimen- 

 sions. He limited himself even to two sets of experiments : he turned 

 the fresh- water polyp outside in, and he multiplied it hy cutting it up. 

 These experiments upon this little creature, which few persons had 

 seen, have sufficed to secure immortality to his name. Tremhley was 

 tutor to the two sons of Count de Bentinck. He made his observa- 

 tions at the country-house of the Dutch nobleman, and he had, as he 

 assures us, " frequent occasion to satisfy himself, in the case of his 

 two pupils, that we can even in infancy taste the pleasures de- 

 rivable from the studies of Nature !" Let us hope that this thought, 

 uttered by a celebrated naturalist, who spoke only from what he knew 

 himself, may remain engraved on the minds of our younger readers. 



Trembley established by his observations, a thousand times repeated, 

 that Hydra viridis can be turned outside in, as completely as a glove 

 may be, without injury to the animal, which a day or two after this 

 revolution resumes its ordinary functions. Such is the vitality of these 

 little beings, that what was once the outer surface soon fulfils all 

 the functions of a stomach, digesting its food, while the intestinal 

 tube expanding its exterior performs all the functions of an outer 

 surface ; it absorbs and respires. But we shall leave Trembley to relate 

 his very remarkable experiments. " I attempted," he says, " for the 

 first time to turn these polyps inside out in the month of July, 1741 

 but unsuccessfully. I was more successful the following year, having 

 found an expedient which was of easy execution. I began by giving 

 a worm to the polyp, and put it, when the stomach was well filled, 

 into a little water which filled the hollow of my left hand. I pressed 

 it afterwards with a gentle pinch towards the posterior extremities. 

 In this manner I pressed the worm which was in the stomach against 

 the mouth of the polyp, forcing it to open continuing the pinching 

 pressure until the worm was partly pressed out of the mouth. When 

 the polyp was in this state I conducted it gently out of the water, 

 without damaging it, and placed it upon the edge of my hand, which was 

 simply moistened, in order that the polyp should not stick to it. I 

 forced it to contract itself more and more, and, in doing so, assisted in 

 enlarging the mouth and stomach. I now took in my right hand a 

 thick and pointless boar's bristle, which I held as a lancet is held in 

 bleeding. I approached its thicker end to the posterior extremity of the 

 polyp, which I pressed until it entered the stomach, which it does the 



