1888.] MICEOSCOPICAL JOUENAL. 223 



nerets, from which issue the threads to form the web. He also discovered 

 the spider's poison-glands, and the peculiar, comb-like arrangement of the 

 claws. These toothed claws are shown magnified in fig. 5, with a part of 

 the spider's hairy leg. By some it is supposed that these combs are used by 

 the spider to cleanse her body ; others think that they help in the weaving of 

 the web. 



The people of that time seem to have been painfully ignorant. Among 

 other notions which now appear laughable was the belief that cochineal was 

 the dried fruit of a tree ; and until our Dutcb microscopist examined this 

 queer fruit and decided it to be a dried insect, nobody seems to have thought 

 of questioning the popular theory. He believed in using his eyes, and when 

 they failed him over the minute things of nature he made a microscope and 

 brought that to his aid. His e3'es were the first to see that each human hair 

 is solid, not the hollow tube that everybody then supposed it to be. While 

 those thoughtless people believed that fleas could be formed from a little 

 heap of moist dust in a warm place, he proved that such a thing, is impos- 

 sible, for he discovered that fleas lay eggs. The common muscle, too, was 

 believed to be formed from the mud it lives in, but Leeuwenhoek laughed at 

 such an idea. He said that if so small an animal as a muscle could be made 

 from a handful of mud so could a whale, but that he did not believe in any 

 such foolishness. Then he set to work to find the muscle's eggs and suc- 

 ceeded. 



It is neither possible nor desirable to mention a hundredth part of this 

 famous man's discoveries. The purpose in selecting those here referred to 

 is to point out for the encouragement of the amateur microscopist a few at- 

 tractive objects, and to show him that an abundance of microscopical work, 

 important work too, can be done with what may seem to be a very poor 

 outfit. It is not so much the tools that make the result, as it is the perse- 

 verance and energy and brains behind the tools. 



REPORTS OF RECENT ARTICLES. 



The Growth of Jelly-fish. — Dr. W. K. Brooks, in the September and 

 October numbers of the Popular Science A/ofzt/ify, presents a review of the 

 morphology of certain of the Hydromedusae, which is of far greater interest 

 than much of the popularized science because it states the result of the latest 

 researches of a great morphologist with regard to the Hydrozoa. The two 

 articles make a fascinating chapter in zoology brought easily within range of 

 every intelligent reader. The purpose of the. articles is to show the meaning 

 of the hydroid stage in the life-history of Hydrozoa. It was once supposed 

 that the Hydroid was an adult animal ; later, it was noticed that free medusas 

 arose from many ; that some exhibited a hydroid condition of great elabo- 

 rateness and a medusa stage of but slight comparative duration. Dr. Brooks 

 argues from the case of Cunina that the hydra stage of the animal is to be 

 regarded as a larval stage of a former developmental history which it rapidly 

 passed through to reach the adult free-swimming medusa condition. That 

 circumstances have in the cases of some of the descendants of such an ancestor 

 made it favorable for them to remain longer in this larval condition, and even 

 to specialize from it several forms, as the feeding protective root and blasto- 

 style polypes of some very complete colonies, and even in some instances to 

 remain in the larval stage permanently and not develop into the medusoid stage 

 at all. This view of the matter gives satisfactory value to all the varied forms 

 of hydromedusae as no other view of the meaning of their difterence has done. 



