March 1, 1886.] 



KNO^A/'LEDGE ♦ 



145 



plate armonr than mail, and the term loricate which has 

 boen given to tlu'tn is scarce!}' appropriate. Those with 

 no such defence have been named illoricate. Then come 

 the Tube Dwellers, mostly- living in gelatinous vessels like 

 pastrycook's ji'.rs ; but in the case of Melicerta making 

 conical bricks of a yellow colour, and building them up 

 into a pretty tower, widening from the base to the toji. 



As an aid to the study of Ixotifers : — 



1. 



0. 



Kig. \.— Rotifer citrlnus, yellow Philodim, from (iosse, Tenby. 

 Figs. 2 and 3.— Its Ciliary wreath, vertical and side views. 

 Fig. 4. — Its Tropin (gizzard). 

 Fig. 5. — Its Tail foot. 



N"o formal arrangement of rotifers as yet made is 

 satisfactory, but any one of them may help the student 

 to name a sjiecies. Dr. Hudson tries his hand at a new 

 distribution. His lihizota are those fixed in their adult 

 stage. Bddloida holds those which both swim and 

 crawl, but thej- are not sufficiently leech-like to make the 

 name appropriate. Then come I'lo'ima, which he trans- 

 lates as " seaworthy," suggesting, unintentionally, that 

 they are marine. The term indicates ship manage- 

 ment, and does not well fit. The last group in his scheme 

 is called Scirtopoda, not a bad name for those that can 

 skip, but he excludes most that do so, and puts only one 

 remarkable skipper, Pedalion, in this order. It is only 

 fair, however, to Dr. Hudson to note that he points out 

 important correlations between the ciliary organs and the 



feet of his various orders, and also of their mouth 

 structure. The ciliary organs of these creatures are very 

 difficult to get a thorough notion of. They are u.sually 

 seen, more or loss, in profile, but opportunities should be 

 sought to obtain vertical view.s, and for this purpose it is 

 often convenient to use a low power and a deep eye- 

 piece, as the greatest penetration results from this plan. 



The .so-called gizzard is the next organ of importance 

 the observer should study after the ciliary wreath. It 

 varies from complex developments, through various 

 str.ges to conditions in which its resemblance to the higher 

 forms disappears. One of the most skilful researches 

 in micro.scopy will be found in papers by Gosse (Philo- 

 sophical Tv;'.nsactions for Februrry :>jnd M",rch, 1S.").5), 

 describing and figuring no less than eighty-five distinct 

 sets of m".nduc:',tory (chewing) organs of Rotifers. Some 

 remarks on these organs will be made in a succeeding 

 paper. They should be studied in action, and also when 

 freed from muscular and other matter by a drop of potash 

 solution, which dissolves it away, and leaves the hard, 

 glassy material, probably a form of chitin, quite clear. 

 The Liquor 2}otassce of the chemists' shops, diluted with 

 four or five times its bulk of water, answers the 

 purpose. 



Recurring to the now work, it should be known that 

 Mr. Gosse and Dr. Hudson have each for many years 

 been collectors and observers of Rotifers, and between 

 them are able to offer a more perfect monogram than iiny 

 single authority could have supplied. Mr. Gosse's skill 

 in making beautiful and accurate drawings is too well- 

 known to need mention, and Dr. Hudson has won dis- 

 tinction in the .same line. Their joint laboiirs result in a 

 truly splendid work. 



STORY OF THE MOON,* 



I HE RE are few points in modern scientific 

 inquiry more important or more interest- 

 ing than the application of each newly 

 recognised truth to all the varied matters 

 on which it bears. The most striking 

 example of this process may be found 

 in the application of spectroscopic analysis 

 to the heavenly bodies ; only in this case it chanced that 

 though spectroscopic analysis is in reality an optical 

 method of pursuing chemical inquiries, it was originally 

 (counting from the detection of the dark lines in the 

 spectrum) suggested by astronomical research. Men 

 inquired into the meaning of the dark lines in the solar 

 spectrum long before they had any idea that in the 

 spectral analysis of light they had a most effective method 

 of chemical research. It seemed natural enough, then, 

 in that case, to apjily the principles discovered in the 

 laboratory to the work of the astronomer in the obser- 

 vatory. Birt with many discoveries made in special lines 

 of research this has not been the case. The workers in 

 one field have been tou busily employed to note either on 

 the one hand the value of their results for other fields 

 than their own, or on the other, the advantage they might 

 obtain from employing in their own field other workers' 

 results. In this way many important discoveries have 

 been missed or delayed. Hence the necessity, which 

 Sjiencer and others have pointed out, for scientific 

 over.seers, who, not working specially in any field, but 

 having a general knowledge of what is going on in all, 



* " The Jloon ; considered as a Planet, a World, and a Satellite." 

 By James Nasiuyth, C.E., ami .lames Carpenter. (Miiiiay; 

 London.) 



1) 



