1895. NOTES AND COMMENTS. 151 



proved baffling, but was later recognised. Altogether it would 

 appear that spiders are by no means so deficient in sight and in the 

 power of differentiating colour as has been urged in some quarters. 

 But whatever may be the ultimate value of Mr. and Mrs. Peckham's 

 paper, there is no manner of doubt that it is exceedingly interesting 

 reading. It is to be found in vol. x. of the Transactions of the Wisconsin 

 Academy of Sciences. 



Comparative Edibility. 



With reference to the note in our February number on warning 

 colours and edibility, Mr. O. H. Latter has kindly sent us the follow- 

 ing observation. He writes : — " It is well-known, and I have myself 

 observed, that all our 'Cabbage' Butterflies are immune from attacks 

 by birds, presumably because of some unpleasant taste or smell. 

 Wasps, however, have twice been observed by me in the act of de- 

 vouring these butterflies. Earwigs, too, which undoubtedly possess 

 an unpleasant smell when irritated, fall victims to wasps, in spite of 

 their malodorous attributes." 



The Origin of Oolite. 



In the last number of Natural Science we referred to a paper 

 by Mr. G. F. Harris on the " Analysis of Oolitic Structure " ; 

 curiously enough, a -week later, Mr. E. Wethered made a communi- 

 cation to the Geological Society on a somewhat similar subject, only 

 that the last-mentioned author laid emphasis on the origin of the 

 granules. Mr. Wethered has " long entertained the opinion that all 

 oolitic granules are of organic origin, but has not, up till now, been 

 in a position to prove this." The class of evidence laid before the 

 Society mainly consisted of micro-photographs of sections of pisolites 

 and oolites, and we must say, that, like many of the speakers who 

 joined in the discussion, we failed to see the proofs referred to. The 

 first few slides shown, appertaining to pisolite, were convincing 

 enough, if a series of vermiform tubules could be taken as evidence 

 of the origin of the granules themselves. That these tubules are the 

 work or the remains of organisms, few would care to dispute. But 

 when the author desires us to see tubules in certain of the oolitic 

 granules, we draw the line, and ask for further proofs. We do not 

 suggest, for a single moment, that with the " eye of faith " they 

 could not be detected on two or three of the slides of oolite ; but it 

 struck us that much of what we saw could be explained very well 

 indeed as due to ordinary chemical action, while several of 

 the structures shown and referred to as proofs of organic origin 

 appeared to be much more like the results of alteration in the granules 

 since they were formed. For a hypothesis to succeed, it is necessary 

 that all the facts ascertained shall be concordant with it ; we do 

 not wish to convey the idea that the origin of oolitic granules, 



