HARDWICKE'S S CIE NCE -GOSSIP. 



257 



sponge - cells five found which contain colourless 

 granules, corresponding to the green-coloured gra- 

 nules of the green sponge particles. These are less 

 definite in their form than the other. It has been 

 found that in the orchid Neoitia, where chlorophyl 

 is absent, a green colour may be developed by the 

 action of strong sulphuric acid, and Mr. Laukester 

 has found that the same thing is true of the colour- 

 less specimens of SponglllafinnatiUs. In the latter 

 the green is fully as intense as in natui-ally green 

 specimens. He thinks the colourless parts are 

 those which first turn green, though after the reagent 

 has acted, the whole mass of coagulated sponge- 

 sarcode is uniformly impregnated with a green 

 colour. Mr. Lankester has heard that Spongilla 

 contains a starch-like body, and asks whether this 

 is so. Perhaps some of our microscopical readers 

 may assist in this matter. Anyhow, the above 

 observations tend to show that chlorophyl in 

 Spcngilla, as in the higher plants, is preceded by a 

 distinct chlorophyl-evolving substance, which is 

 calourlcss. 



ZOOLOGY. 



" SoMGS OF PisiiES."— A learned and highly 

 readable article on this subject, by Mr. John C. 

 Galton, F.L.S., appears in the last number of the 

 Popular Science Uevieio. Two other articles in this 

 capital magazine are worth careful perusal— "The 

 Thermometer as a Companion in Daily Life," by 

 Professor A. H. Garrod, one of our most promising 

 young naturalists ; and another, on " The Vegetable 

 Cell," by Mr. A. W. Bennett, the well-known 

 botanist. 



Spidxks' Webs and Spi?;neiiets. — Since the 

 above article was sent, a further examination of a 

 Clnijld's web leads me to think that I have fallen 

 into error when describing it, from the bad habit 

 of " jumping to conclusions." Under my highest 

 power (a quarter-inch) the fourth threads of a 

 Ciniflo's web present the appearance of being com- 

 posed of a multitude of threads, as I have stated, 

 which they also do with a power of 320 diams., but 

 on increasing the magnification to 750, this appear- 

 ance vanishes, and they, i.e. the "film," looks as if 

 it were simply mucus. A few days ago I stained 

 some of the web with magenta, and the examination 

 of these stained specimens with a quarter-inch 

 objective confirms me in the idea that the film is 

 nothing but mucus, though 1 am not yet sure that 

 this is the case. I hope soon to have another op- 

 portunity of examining my slides with a power of 

 750, which I think, now that I have stained the 

 threads, will settle the point. Figs. 120 and 122 are 

 both magnified IGO diameters : this was not stated 

 in the foot-note.— i7. /. M. Underhill, Oxford. 



Spiders' "\Yebs and Spinnerets.— As I have 

 the pleasure of knowing Mr. John Black wall, the 

 eminent arachnologist, I sent him last month'.s 

 number of Science-Gossip, containing Mr. Under, 

 hill's paper on the " Spinnerets of Ciniflo." 1 

 examined this object some years ago, when visiting- 

 Mr. Black wall, and was fortunate enough to see it 

 as Mr. Underhill describes it, except that I dis- 

 tinctly saw the extra pair of spinners covered with 

 papillce. and not holes. Mr. Blackwall saw them 

 also, and I enclose a letter I received from him on 

 the subject. — W. Statham. 



The September number of Science-Gossip 

 which accompanied your kind letter came safely to 

 hand, and I am much obliged to you for it. Mr. 

 Underbill's concluding part of the article on 

 " Spiders' Webs and Spinnerets " is especially inter- 

 esting as supplying additional evidence, based on 

 anatomical (details, of the soundness of my views 

 relative to the fourth pair of spinners, — calamistrum, 

 and snare of Cinijlo afro.v, derived from careful 

 observation and experiment, and confirmed by the 

 inspection of these structures under your powerful 

 microscope. This is highly satisfactory, as the 

 correctness of my statements in connection with 

 these subjects has been called in question both by 

 native and continental zoologists. The nomenclature 

 adopted by Mr. Underhill differs somewhat from 

 that employed by me ; the parts termed ' spinnerets ' 

 by him I name ' spinners ' or ' spinning mammulse,' 

 and the delicate tubes from which the viscid secre- 

 tion that forms the lines of spiders proceeds, the 

 ' spinning-tubes ' or ' spinnerets.' Mr. Underbill is 

 certainly mistaken in supposing that the fourth pair 

 of spinners are not provided with spinning-tubes, 

 but are merely perforated ; and he is also in error 

 in thinking that the lines constituting what I 

 denominate the floccuU, are spun at the same time 

 as the foundation-lines to which they are attached ; 

 this, however, is not surprising, as he admits that 

 he has never seen the spider use its calamistrum. I 

 should much like to know what he says of the 

 snares of the Epe'irce or geometric spiders.— t7o//« 

 Blackwall. 



Changes of Skin in Caterpillars.— Those 

 who have reared caterpillars from the egg to matur- 

 ity are well acquainted with the fact that they pass 

 through various changes of skin, called scientifically 

 the ecdyses of these insects. It is a matter of some 

 interest ; and in regard to which I should be glad 

 to elicit the opinion of others, who have had oppor- 

 tunities of observing many species; whether the 

 number of these changes is fixed and invariable in 

 each. As is pretty well known by entomologists, 

 hairy larvae undergo more frequent changes ; in some 

 species they reach the number of seven or eight. 

 Three or four changes of skin appear to be about 

 the average with the bulk of the smooth larvae, ex- 



