HARDWICKE'S SCIENCE-GOSSIP. 



275 



there are auy number of minute insects having no 

 such tarsal apparatus, which are equallj' indifferent 

 to the laws of gravitation so far as walking on 

 smooth, upright surfaces, or on the ceiling, is con- 

 'Cerned. In reality, these pads are thickly beset on 

 the lower surface with short hairs, most of which 

 terminate in a minute expansion kept continually 

 moist by an exuding fluid— a sort of perspiration. 

 Take the human hand, moistened by perspiration or 

 other means, and draw it, with slight pressure, first 

 over a piece of glass or other highly-polished surface, 

 and then over something that has a rougher surface, 

 such as a planed board, a papered wall, or a velvety 

 fabric, and you will experience much greater ad- 

 hesion to the smoother objects, and may understand 

 the important part which these moist pads play in 

 the locomotion of the fly ; they also act, in part, 

 like the cushions of a cat's paw in protecting and 

 preventing abrasion of the claws, which are very 

 useful on the rougher surfaces, where the pads are 

 less serviceable. 



Now, compared with JIusca domestica, the claws 

 of Sarcopliaga Sarracenice are much the longest and 

 strongest, and the pads much the largest, presenting 

 three or four times the surface. These differences 

 are, I think, sufficient to explain the fact that while 

 the common fly walks with slippery and unsteady 

 gait on the smooth pubescence (the retrorse nature 

 of this pubescence sufficiently explaining the down- 

 ward tendency of the movements), its sarcophagous 

 wngener manages to get a more secure footing ; 

 for not only does the latter present a larger adhesive 

 surface, but the longer claws are more likely to 

 reach beyond the pubescence and the bristles, and 

 fasten to the cellular tissue of the leaf beyond. j 



In answer to the second question, I can only say 

 that there is nothing exceptional in the power of the 

 larva to withstand the solvent quality of the fluid ; 

 it is, on the contrary, in accordance with the facts 

 known of many species of Muscidai and OEstridse, 

 some of which, like the well-known horse-bot, revel 

 in a bath of chyme, while others are at ease in the 

 intestinal heat of other warm-blooded animals. It 

 is also well known that they i,will often live for 

 hours in strong liquids, such as alcohol and turpen- 

 tine. 



To one accustomed to seek the why and where- 

 fore of things, the inquiry very naturally arises as to 

 whether Xauthoptera and Sarcophaga play any 

 necessary or important role in the economy of Sar- 

 racenia. Speaking of the Sarcophaga larvag, Mr. 

 Eaveuel asks, " May it not do some service to Sar- 

 racenia, as Pronuba does to Yucca ? " And if so, 

 may not all this structure for the destruction of 

 insects be primarily for his benefit ? Can he be 

 merely an intruder, sharing the store of provision 

 which the plant, by ingenious contrivance, has 

 secured for itself, or is he a welcome inmate and 

 profitable tenant ? Self-fertilization does not take 



place in Sarracenia, and the possibility that the 

 bristly Elesh-fly aids in the important act of pollina- 

 tion lends interest to the facts. No one has wit- 

 nessed with greater pleasure than myself the unpulse 

 which Darwin has of late years given to such in- 

 quiries ; but we should be cautious lest the specula- 

 tive spirit impair our judgment or cur ability to 

 read the simple lesson of the facts. My own con- 

 clusions summed up are : — 



1. There is no reason to doubt, but every reason 

 to believe, since the observations of Dr. Mellichamp, 

 that Sarracenia is a truly insectivorous plant, and 

 that by its secretions and structure it is eminently 

 fitted to capture its prey. 



2. That those insects most easily digested (if I 

 may use the term) and most useful to the plant are 

 principally ants and small flies, which are lured to 

 their graves by the honeyed paths ; and that most of 

 the larger insects, which are not attracted by sweets, 

 get in by accident and fall victims to the peculiar 

 mechanical structure of the pitcher. 



3. That the only benefit to the plant is from the 

 liquid manure resulting from the putrescent captured 

 insects. 



[Mr. Ravenel, in making a transverse section near 

 the base of the young leaf, noticed large tubular 

 cells passing down through tho petiole into the 

 root, and much of the liquid manure may possibly 

 pass through these into the root-stalk.] 



4. That Sarcophaga is a mere intruder, the larva 

 sponging on and sharing the food obtained by the 

 plant, and the fly attracted thither by the strong 

 odour, as it is to all putrescent animal matter or to 

 other plants, like Stapelia variegata, which give 

 forth a similar odour. Tliere is nothing to prove 

 that it has anything to do with pollination, and the 

 only insect that Dr. Mellichamp has observed about 

 the flowers with any frequency, is a Cetoniid beetle, 

 the Euryomia melanclwlica. 



5. That Xauthoptera has no other connection with 

 the plant than that of a destroyer, though its greatest 

 injury is done after the leaf has performed its most 

 important functions. Almost every plant has its 

 peculiar insect enemy, and Sarracenia, with all its 

 dangers to insect-life generally, is no exception to 

 the rule. 



6. That neither the moth nor the fly has any 

 structure peculiar to it, that enables it to brave 

 the dangers of the plant, beyond what many other 

 allied species possess. 



MICROSCOPY. 



New Diatoms. — A new genus and several new 

 species of diatoms have been figured and described 

 by Mr. P. Kitton, of Norwich, in the November part 

 of the Monthly Microscopical Journal. The more 

 remarkable forms were found in a gathering made 



