April i,, 1872] 



NATURE 



443 



discussion of the Origin of Insects. The general question of the 

 Annulosa obviously includes that of Insects, and I therefore 

 desire to correct this statement, and to refer your readers to a 

 paper by me on Chcetogaster and .^lolosoma, published in the 

 "Linnean Transactions," vol. xxvi, (read Dec. 1867), in which 

 I have more than alluded to Mr. Spencer's views, and have 

 offered some suggestions on the morphology of the head, and as 

 to the unisegmental Annulose ancestor. Mr, Wallace quotes 

 from this paper in reference to Chcetogaster, though from the 

 context it would appear that he is quoting from Professor Owen. 



Since the researches which have rendered Mr. Wallace's name 

 one of the first among living zoologists have not led him into 

 practical anatomical and embiyological studies, I may venture to 

 add one or two strictures upon his statements relating to such 

 matters. In the first place, those who are engaged in the study 

 of insect embryology are not ignorant of Mr. Spencer's or 

 similar views ; the wide-spread study of his works in England 

 and America, and of Haeckel's general morjAology in Germany, 

 is sufficient guarantee of this. But even if it were as Mr. 

 Wallace supposes, he has not, in the extract given in Nature, 

 shown at all how Mr. Spencer's views on aggregation are to 

 influence the study of the embryology of insects. Of course, the 

 general theory of somites has immense importance in all studies 

 relating to the Annulosa, but in what way the particular form of 

 it, due to Mr. Spencer, can influence conclusions drawn from the 

 observation of the manner in which insects develop from the 

 egg, Mr. Wallace does not explain. Whether, admitting or 

 denying the truth of Mr. Spencer's or Prof Haeckel's views, it 

 would be equally conceivable, did the observed facts point in 

 either direction — that the ancestry of insects is to be traced to a 

 simple nauplius-form or to a multi-segmental Annelid-like pro- 

 genitor, the question of segmentation is not finally settled, 

 though it is largely elucidated by the doctrine of Mr. Spencer. 

 It is no doubt an instiiictive point of view to take — that seg- 

 mentation is an arrested production of zooids. but it is equally 

 true that the production of zooids is an exaggerated segmenta- 

 tion. We have no grounds for assuming the one more than 

 the other as the essential process ; they are both phases of the 

 same process. The fact appears to be that in certain masses of 

 organised matter, on their reaching a certain limit of growth, 

 "polarities," which were hitherto held in one system, break up 

 into two and so on. The simplest case of this is cell-division, 

 but whether the systems separate entirely, as in simple fission, or 

 remain associated, as in the cleavage of the egg and in the seg- 

 mentation of the Annulosa, depends on another factor, a cohe- 

 sive or integrating force proper to the growing mass. 



In the present state of knowledge upon the subject, the assump- 

 tion adopted and held of so much importance by Mr. Wallace — 

 that the Vertebrata do not exhibit a segmentation of the same 

 kind as that of the Annulosa, is by no means justified. Though 

 much of their jointed iterative structure may probably be due to 

 that kind of adaptation which Mr. .Spencer so justly distin- 

 guishes as " superinduced segmentation," yet that there is a funda- 

 mental bud-segmentation, or segmentation of growth identical 

 with that of Annulosa, is in the very highest degree probable. 

 And even as to the Chiton, which Mr. Wallace quotes from Mr. 

 Spencer as quite certainly an example of superinduced segmenta- 

 tion, I think that had he examined the grounds for making such 

 a statement, he would have hesitated. The larva of Chiton is 

 identical with that of an Annelid, and its segmentation makes 

 its appearance in the same way. Why should there not be seg- 

 mented molluscs? It is necessary most constantly to bear in 

 mind, when considering this matter of segmentation, the possi- 

 bility of the partial or complete obliteration of segmental 

 characters due to tertiary aggregation, and their modification in 

 most various ways in the evolution either of an individual or of a 

 group. 



Further, as to Mr. Wallace's expressions with regard to the 

 segmentation of insects. From what was said above as to the 

 relation of segmentation and zooid production, it follows that 

 the conception of segmentation is erroneous which leads to 

 ascribing to insects peculiar physiological or psychical properties 

 on account of their being composed of "a number of indivi- 

 dualities fused into one." This expression should not be allowed to 

 lead to wider conclusions than those it formulates. As a matter 

 of fact, insects are not a number of individualities fused into one, 

 but rather one individuality partially (and as a reminiscence 

 rather than actually) broken up into many, this partial breaking 

 up being due to the mechanical properties of its tissues at a certain 

 period of development. 



If, by the "spiracles" of Annelids, Mr. Wallace means the 

 segmental organs, it should be clearly stated that the identity of 

 these with the trachea; of insects has not yet been in any way 

 proved. The comparison of the mode of development of these 

 two sets of organs is just one of the points upon which embryo- 

 logists are now at work. 



Last'y, the researches of the last fifteen years do not, I venture 

 to submit, lead to the conclusion adopted by Mr. Wallace, that 

 the parthenogenesis of the higher Annulosa is analogous to or 

 identical with gemmation as opposed to sexual reproduction or 

 digenesis, but to the conclusion which is exactly opposed to this, 

 namely, that it is identical with digenesis in all particulars but 

 the absence of the male element. 



Naples E. Ray Lankester 



Adaptive Coloration, Phosphorescence, &c. 



No one who has watched a very young hare stealing from a 

 green covert to brown soil, and observed its cunning movements 

 there when alarmed, can for a moment doubt the value of colour 

 as a protection to the higher animals. 



The remarks by Mr. E. S. Morse in Nature of last week 

 bring to my recollection a good instance (among invertebrates) 

 which occurs on the reddish granite of Cobo Bay, Guernsey. 

 There Trochus lineatus especially abounds on the bare parts of 

 the rocks between tide-marks ; and every observer must be at 

 once struck by the remarkable fitness of the mollusk for its 

 peculiar site. 



Mr. Darwin in truth says,* "It would not, for instance, occur 

 to any one that the perfect transparency of the Medusae or jelly- 

 fishes, was of the highest service to them as a protection ; but 

 when we are reminded by Hackel that not only the Medus.-e, but 

 many floating muUusca, crustaceans, and even small oceanic 

 fishes, partake of this same glass-like structure, we can hardly 

 doubt that they thus escape the notice of pelagic birds and other 

 enemies ;" but he makes no mention of the gorgeous colouring 

 of some of these swimming jellies, nor is there any allusion to 

 their remarkable property of phosphorescence. The transparency 

 of the British Salpa; does not prevent their being attacked by 

 sea-birds, which hover in multitudes over them, masses of 

 Medusie and other Hydrozoa, and a few minute fislies. 



If instead of promulgating the visionary idea that the abysses 

 of the ocean depended for tfieir light on phosphorescent animals, 

 the dredgers+ in the PorcKpine had applied the notion that the 

 various luminous marine animals used their light to attract each 

 other, so that the most luminous might have a better chance of 

 continuing the race, they would have been able to say more in 

 its favour, without, at least, running counter to established facts. 



Murthly, March 26 W. C. McIntosh 



The Aurora of February 4 f 



An aurora of a very unusual splendour for the latitude was 

 seen here on Sunday evening February 4, 1872. The sky, 

 extending in azimuth over 197° from N. E. to nearly W. S.W., 

 was generally illuminated. The brilliance of the glow varied 

 considerably in different directions from time to time during the 

 night. On the south horizon there was a bright bluish segment 

 of light, whose position in azimuth and brilliance varied slightly 

 from time to time. The streamers were well seen, and their 

 convergence towards the point to which the south pole of a 

 magnet is directed could be most distinctly traced. The streamers 

 extended at about nine o'clock to the constellation Orion, and 

 Sirius was well within the auroral glow. With a spectroscope I 

 saw one bright line in the spectrum of the auroral light, but the 

 spectrum was too faint to .allow of any successful attempt to de- 

 termine the refrangibility of the light. Unfortunately our mag- 

 netical equipment is such that I can give no information respect- 

 ing the extent of the magnetical disturbance at the time. The 

 aurora was seen as far north as Bloemfontein, latitude 29° 8' south. 

 A faint aurora was seen here in October 1870, but no such 

 aurora as that of February 4, 1S72, appears to have been visible 

 for at least fifty years. The aurora was well seen over a large 

 portion of the colony, and considerably frightened the natives." 



E. J. Stone 



Royal Observatory, Cape of Good Hope, Feb. 19 



* " Descent of Man," vol. i., p. 322. 



t Not. however, Mr. Jeffreys 



X Communicated by the Astronomer Royal. 



