126 



HARDWICKE'S SCIENCE-GOSSIP. 



my interest being thoroughly aroused, I determined 

 to prosecute my search. For this purpose a number 

 of ash-branches were selected, and carefully laid on 

 one side. A cursory glance at these showed nothing 

 at all abnormal or noticeable, but a more careful 

 examination disclosed a number of small ridges of 

 discoloured skin traversing the branches in various 

 directions. Taking off the bark at these points, the 

 main passage before-mentioned was exposed to view. 

 On tracing this up or down the stem it was always 

 found to terminate below an old leaf-scar. Finding 

 this, I now examined the leaf-scars, and in a majority 

 of cases found a small hole filled below with fine 

 dust. Detaching the skin at this point a small run 

 was visible, passing just below the scar to the right 

 or left ; and when clear of it branching off in two 

 opposite directions up and down the branch (fig. 89), 

 but usually more or less spirally arranged. At the 

 entrance to this passage was generally found a small 

 beetle, and another some distance along. There 

 were mostly two, but whether they were male and 

 female, or whether they were both females acting in 

 concert I was not able to determine. The diameter 

 of the principal passage is about i-i6th in. The 

 beetle I found to be Hylisinus fraxini. 



It appears to be very prolific, and must be very 

 destructive to the trees it attacks. In the cases I 

 examined there were usually from 60 to 80 diverging 

 passages, and at the end of each, as before-stated, 

 was a fat larval beetle, busily engaged excavating for 

 its daily rations. In many branches, almost every 

 node was the starting-point for these channels, and 

 the amount of mischief done to the tree may well be 

 imagined when we bear in mind the numbers found 

 in each run, and their method of working side by 

 side so closely as to all but completely sever the bark 

 from the wood. After examining a great number, a 

 few specimens were put on one side for the purpose 

 of watching their progress towards maturity. 



On the 28th August the now-transformed larvae 

 began to emerge in the imago form, i.e., as perfect 

 winged beetles. They were pretty little insects, 

 varying considerably in colour, some being much 

 lighter than others, and most distinctly clouded. 

 On raising the bark I found a great number still 

 occupying their snug quarters, where they had fared so 

 comfortably during their early days, and where they 

 had undergone their final change preparatory to 

 entering upon a more active and greatly extended 

 sphere of action. I now found that, prior to under- 

 going their first metamorphosis, i.e., assuming the 

 pupa form, they sink for themselves, at the end of 

 their respective galleries, a comparatively deep pit, in 

 which the change takes place. In these pits they 

 may be found in August ready to make their way out 

 previous to setting up housekeeping on their own 

 account. 



Noel Humphreys gave an interesting account of 

 these beetles in the pages of the "Intellectual Ob- 



server," in 1862. He there states that they attack 

 the elm as well as the ash, and that their ravages are 

 often terrible. The ash, however, is their favourite 

 tree, as may be gathered from the specific name 

 {Fraxini) of the insect. 



Having thus learnt how numerous and destructive 

 these insects are, and remembering that in a row of 

 ash-trees that I passed daily some were flourishing 

 grandly while others were dead or dying, I determined 

 to ascertain whether these beetles had anything to do 

 with the matter. On examining the dead and dying 

 trees, I found them literally riddled with minute 

 shot-like holes — the significance of which was now 

 only too plain to me. I had often noticed the dif- 

 ference between these trees, whose conditions, as to 

 soil, climate, &c, appeared to be identical, and 

 wondered what could be the cause of the death of 

 these, while those by their side grew vigorously. 

 Had I noticed these holes a few weeks earlier, their 

 meaning would have been hidden from me, but now, 

 from the study of a few faggot-sticks I was able to 

 understand most clearly what had been going on 

 beneath the bark of these unfortunate trees, and why. 

 they had gradually, without any apparent cause, 

 drooped and died, branch by branch and limb by 

 limb, until a giant mass of mere dry sticks remained, 

 rearing its weird and awe-inspiring form against the 

 sky. 



Thus, from the careful examination of a " faggot - 

 stick " I gathered the life-history — or at all events the 

 leading facts in the life-history — of a pretty little 

 British beetle, which undoubtedly plays an important 

 part in the "struggle for existence," which ultimately 

 results in the "survival of the fittest," that has to 

 compete in common with every other member of 

 the organic world. 



Rochester. John Hepworth. 



WHAT A DIATOM IS. 

 ( Continued from page 107. ) 



IT is the act of generation that brings back the 

 normal size of the frustule, already reduced in 

 dimensions by repeated deduplications ; if this did not 

 take place, the diatom would (theoretically) at last 

 become a mere atom — a circumstance which never 

 takes place. 



The act of generation, properly so called, may be 

 said to consist in all organisms of a simple amalgama- 

 tion of two more or less distinct particles of proto- 

 plasm. The diatoms are no exception to this rule, 

 and with them this union comprises either the contents 

 of two distinct frus titles, or of differentiated protoplasm 

 contained in a single frustule. This phenomenon is 

 called the conjugation of the Diatomaceaa. The 

 study of the phenomena of conjugation in some forty 

 species of diatoms, by various distinguished microscopic 

 observers, has not furnished us with such complete 



