HA RD WICKE ' S SCIENCE-GOSSIP. 



65 



consists of a sac whose walls are constructed from the 

 ectoderm cells, and whose interior is formed of the 

 interstitial cells which fill up the spaces caused by 

 the tapering off of the ectoderm cells to the support- 

 ing lamina. These interstitial cells now constitute 

 germinal ones, and develop into spermatozoa, re- 

 sembling those of mammalia, except for the tails, 

 which are undulate. They are liberated by the 

 bursting of the apices of the cells. 



Near the foot a large projection arises. This is 

 the ovary. At first it consists of many germinal cells, 

 but later on of only one, which is now called the ovum. 

 The spermatozoa reach this latter by the vibratile 

 motion of the tail, and impregnation takes place. 

 Subsequently the ovum is detached from the body, the 

 sac becomes ruptured and the young Hydra escapes. 



The most surprising thing connected with the 

 Hydra, however, is the power of reproducing lost 

 parts, and this it was that caused such excitement 

 When Trembley announced his discovery. If the 

 body be cut into two or more parts, provided each 

 severed part contain ectoderm and endoderm cells, 

 the parts will supply their complements. Thus, 

 sever a Hydra into two portions by a transverse cut ; 

 the lower will produce a new pair of tentacles, the 

 upper a new foot and archenteron. You may cut it 

 into a hundred pieces, and each part will reproduce 

 the parts necessary to form a complete animal and 

 continue to live as though nothing had happened. 

 Slit a Hydra lengthwise through the tentacles and 

 down to the foot, but without quite detaching the 

 two parts. If left alone they will unite and form a 

 perfect being again. Keep them asunder and two 

 Hydras will be perfected on one foot. Slit a Hydra 

 upwards to the base of the tentacles and keep the 

 two portions apart ; two bodies will be formed sur- 

 mounted with ,but one pair of tentacles. Put the 

 body of one into the mouth of another, keep them in 

 position, and they will firmly unite and form a single 

 animal, distinguishable from others only by the 

 double number of tentacles. Cut a tentacle off and a 

 new body and the remaining tentacles sprout from it. 

 This extraordinary power is very wonderful, but 

 never in a natural state does it employ this method of 

 " fission " for reproducing its kind. It was formerly 

 reckoned that a Hydra could be turned inside out 

 like a glove, and continue to live and digest its food 

 in this condition ; but more modern researches have 

 disproved this statement and shown it to be a fallacy. 

 Such, then, is an outline history of what is veritably a 

 green water-dragon. 



Botany has made rapid advances within the last 

 twenty years, and perhaps there is no cheap 

 "Manual" published at that time now in active use 

 except Dr. M. C. Cooke's "Manual of Structural 

 Botany" (London : W. H. Allen & Co.), of which 

 the 37th thousand (revised edition) has just been 

 published. It contains fifteen illustrations. 



SCIENCE-GOSSIP. 



Germs, poisonous and innocent, seem to be present 

 everywhere. On their microscopic backs is placed 

 the onus of a hundred diseases. A fresh one has 

 just been added to the list. Tetanus, or "lockjaw," 

 as that terrible affliction is more popularly called, 

 is now proved to be due to the presence of a virulent 

 micro-organism. Between the infliction of a wound 

 and the development of lockjaw there is sufficient 

 time to allow the spores of this minute organism to 

 develop into bacilli, when the latter produce those 

 distinctive features characteristic of this dreadful 

 disease. The virulence of this organism is only 

 equalled by its wonderful vitality. Thus a small 

 fragment of wood was extracted from the ancle of a 

 child who had died from lockjaw. This fragment 

 was kept for eleven years, when a portion of it, by way 

 of an experiment, was introduced under the skin of a 

 rabbit, and the rabbit died immediately afterwards of 

 tetanus. In the pus or yellow matter of the wound, 

 made by introducing the splinter of tetanised wood, 

 crowds of tetanus bacilli were found. 



Many of our readers are acquainted with the 

 remarkable lens brought out by Mr. Dallmeyer during 

 the present year, and which he calls " telepho- 

 tographic." This long word simply suggests the 

 invention of a lens which can photograph objects at a 

 distance. For instance, at a recent meeting of the 

 Camera Club, pictures were exhibited representing all 

 the details of a building which had been taken at a 

 distance of 500 yards. Two cameras seem to be 

 necessary, one supplied with a long focus landscape 

 lens, and the other with Mr. Dallmeyer's new 

 telephotographic lens. In this way the flame of a 

 common oil lamp placed twenty feet away can be 

 accurately photographed. It is anticipated that before 

 long this new lens will be applied to that deeply 

 interesting department of modern scientific research — 

 stellar-photography. 



A new method of manufacturing glass vessels 

 which will not break under sudden changes of 

 temperature is announced ; the plan adopted being to 

 make the article with an inner layer having a lower 

 co-efficient of expansion than the outer layer. Articles 

 made in this way seem to have the useful qualities of 

 Bastie's " hard glass," without the tendency to spon- 

 taneous explosion ; and the making of them is in most 

 cases easy, as the operator first takes up on his blow- 

 pipe a mass of the glass with the lower co-efficient of 

 expansion, and the more expansive glass is now taken 

 up on the outside of the first by dipping in another 

 pot. 



Chemists rush in where angels fear to tread. To 

 them there is nothing hidden that shall not be re- 

 vealed. In their researches and experiments the 

 word " sacred" is unknown. Here is an instance of 



