Sept. 21, 1883.] 



KNOWLEDGE ♦ 



181 



foreign olyect. The other end contains a central ajierture, 

 or mouth, which leads into the simple sac-like body cavity ; 

 around tlie mouth a circlet of tentacles, or arm-like hollow 

 slender process, are spread out. Careful examination with 

 a high power of the microscope shows that the wall of the 

 body cavity and of the tentacles, which are co;cal prolonga- 

 tions of that cavity, are composed of two layers of cells, 

 constituting an ectoderm and an endoderm ; and that 

 between these there is the early indication of a third layer, 

 or mesoderm, which arises from the basal extremities of the 

 ectodermal cells. This layer is called, after its discoverer, 

 Kleinenberg's neuro-mti.scular layer, because it is supposed 

 that it represents a nascent form of muscular and nervous 

 system combined. 



Many very complicated forms of Ihjdrozoa, which include 

 the peculiar plant-like sea-firs (^Sertularida), and their 

 strange independent reproductive members, termed medu- 

 soids, or jelly-fishes, may be seen in bottles of spirit at the 

 extreme corner of the East Quadrant. These specimens 

 are each worthy of a careful description, so exquisitely 

 have they been prepared. We may state here, without 

 fear of any contradiction, that each specimen in the collec- 

 tion from the Zoological Station of Naples is a masterpiece 

 of museum mounting, and we would therefore draw the 

 special attention of students to this section of the 

 Exhibition. 



In spite of the extreme variety of form exhibited by the 

 Ilydrozoa, the primitive sac-like nature of the organism, 

 consisting of two layers, is never wholly disgnised, and this 

 fact, which was first generalised by Huxley,* has led that 

 eminent observer to make the following statement : — 



" Thus there is a very real and gennino analogy between the adult 

 hydrozobn and the embryoni'i vertebrate animal ; but I need hardly 

 say it by no means justiiies the assumption that the Hydrozoa are 

 in any sense arrested developments ' of higher organisms. All 

 that can justly be affirmed is, that the hydrozoon travels for a 

 certain distance along the same great liighway of development as 

 the higher anima), before it turns off to follow the road which leads 

 to its special destiuation."t 



TRICYCLES IN 1883. 



SMALL WHEELS v. LARGE WHEELS. 

 By John Browning, 



Chairman of the London Tricycle Chih. 



" C1IGMA" has completely missed my point. He has 

 kj evidently written under the supposition that I am 

 advocating theoretically the construction of tricycles with 

 small wheels, whereas I am showing that three or four 

 years ago I was advocating their use theoretically, while 

 now the most advanced and skilful manufacturers are 

 making them, and the fastest and best riders are 

 adopting them, and having proved my case experi- 

 mentally, I have only written with the intention of 

 hastening the inevitable revolution; but I am obliged 

 to my friend " Sigma " for giving me the opportunity 

 of making my views clearer on this subject. He has 

 totally misund(;rstood me, and others may have done the 

 same. He has also completely misrepresented what I 

 have said, though this, I feel sure, he has done un- 

 wittingly. 



I find " Sigma " accusing mo of recommending tricycles 

 which will travel at four or five miles an hour, and, by 

 implication, calling me absurd for doing so. My reply is 

 simply that I have not done so. 



* Proc. Linn. Soc, 1849. 



t " Monograph of the Oceanic Hydrozoa." Eay Society's Pub- 

 lications. 1859. 



I find myself accused also of theorising. I have 

 nowhere referred to theories in my articles, but only given 

 facts, and conclusions which must follow from them. 



Next I am told that it is easier to ride a machine with 

 large wheels at seven or eight miles an hour than a 

 machine with 36-inch wheels at the rate of four miles 

 an hour. I reply that " Sigma " has not tried the ex- 

 periment or he would not say so. / have, and knov} it 

 is not. 



" Sigma " supposes that I recommend small wheels because 

 they are easy, though slow. I do so because, as I state, 

 they are easy 'nid fast. 



The person who begins with one of the small-wheeled 

 machines could, as he wished for more speed, have his 

 machine geared up even to 65 inches if he pleased, at 

 a trifling expense. 



This would avoid all the rapid pedalling " Sigma " 

 declaims against. 



" Sigma " says the machine he rides has .50-inch wheels, 

 is geared up to 60 inches, and yet weighs only 60 lbs. I 

 reply that if it had wheels 40 inches diameter they might 

 be geared up to 60 inches, and the weight of the machine 

 might be reduced to about 40 lbs., and yet be equally strong 

 and it would be faster. 



" Sigma " is an exceptionally strong rider and I am a 

 weak one, but Mr. Nixon, who is a more powerful rider 

 even than himself, will tell him that I gave him the slip 

 in Croydon, not long since, and that he had to ride for 

 half an hour, at the rate of certainly more than ten miles 

 an hour before he could catch me. 



Mr. Nixon had 50in. wheels, and I had 38-in. geared to 

 48-in. 



Had I been riding a machine like his own, Mr. Nixon 

 would have had no trouble in catching me in five minutes. 



No one knows better than " Sigma " how much I have the 

 interests of tricyclists at heart. Surely he may trust me 

 on a mechanical matter not to mislead them. 



The fact that the Coventry " Eotary," one of the fastest 

 machines, has two 20-in. wheels on one side is a sufKcient 

 proof, if any were required, that small wheels will not 

 prevent a machine from travelling quickly. 



Early this year, I had the pleasure of acting as judge in 

 the 100 miles road ride of the London Tricycle Club. 



" Sigma " will not be likely to forget this, as, with a 

 disabled hand and foot and a broken machine, the result of 

 an accident only two days before, he won the 100 miles 

 time medal in an exceptionally plucky manner. 



The first thirty-six miles of road — from Boston to Peter- 

 borough — was so rough that it broke the front wheels of 

 several machines. Rough roads are supposed to be un- 

 rideable by small wheels, yet Mr. Arthur Salmon was 

 amongst the first two or three men in, thoiiyh he wasridiTig 

 a machine with i'2-in. w'heeh. 



A few weeks ago, Mr. A. Salmon and myself rode 65 

 miles in a day together. Mr. Salmon rode his 42-inch, 

 geared up, I believe, to 58, I rode my 38-in., geared to 48 

 in., wo stopped about three hours for rest and refreshment, 

 and I was home before eight o'clock in good daylight. I 

 leave " Sigma " to imagine whether our pace was anything 

 like four or five miles an hour. 



Not a single remark was made about the smallness of 

 our machines by drivers or others, nor has there been either 

 before or since, and I am sure our Editor will agree tliat 

 some D.G.N.F. would, if we looked awkward on them, be 

 sure to tell us so. The L.T.C. is strong in chaff as well as 

 riding. 



Mr. Salmon is 5 ft. 10 in. at least, and finds 42-in. wheels 

 large enough for him. 



In proportion to this, as I am only 5 ft. 4 in., a machine 



