332 



THE AMERICAN 



iKiti^ii and running; uuly uiie-twentieth 

 of ite boughs, is, acconling to the 



11-, in ordinary parlance, the chances 



■h nil improbable event happening. 



\' '\ on the supposition of the tree 



.i\in,i;been takeuat random with- 



1"< II 111 Lr..i: I'.tl.ih. I \iivtUiug into cousideratiuu, we 



niiiy iii.li , Willi a li.-i, , cjf certainty amounting to moral 



cnuvuiioM. ih.ii ii w :i^ iK'i iii'.i-e chance that caused the four 

 oak-iippli-s to i;in\v tip.iii tile large bl.iek oak that I was at 

 this iieriod e.xpi-riniLUtiiijc on, but that they wi're generated 

 by the gall-llius 1 had iiiyself placed there in the preceding 

 aiitiiinn And a similar mode of reasoning will apply to the 

 olh. 1- 1 \pri iiiMiil, tliL- results of which will be subsequently 



'^"iii' iiri.ii , jiiiliaps, who are not familiar with the 

 thiMiy ot rhaiM- ■-;, may consider such odds as those specified 

 iustnow to be iusullicient to produce moral conviction. Yet 

 the very same men, when serving on a jury, will feel no 

 scruple at condemning a prisoner to the gallows for murder, 

 although it i.s mathematically demonstrable that the chance 

 of any supposeil murderer taken at random, who is hung for 

 murder, being really guilty of that murder is only about 1999 

 to 1. .Scarcely a .-iii-U' case .if iiuuder, wli.re ilic prisoner 



subseqnently jirovud to haw bien enliiily innocent of the 

 crime laid to their charge. I am satisfled, on a careful ex- 

 amination of the facts, that out of the whole number of men 

 actually hung for murder, somewhere about 1 in eicry.wio 

 were innocent of the crime for which til. y iilri 1 i ,i,s.- 

 qnently, upon this supposition, the cliaii. ■ .,r ;iii\ ..n. ii|i- 

 posedmurderer, taken indiscriminately IV,. Ml ii., n !im|, i,i;,,s 

 ol men actually bun- r. t mmili r, ]), iiu n, i , hi ju.ii is 

 ""•y »uo> or. in iiopiil i: ,i i h, i 



that he is guilty. Ami mi,, ,i, ,,. , i,,,,,. 



der when the moral i. ,,j ih,ii .:iiilii.,i m,,,, h.il.ly 



very much less than th.^ moral ii.rtaintv of tlu' oak-appk^s 



that 1 ■ 



iiting with having been produced by the 



gall-llies that I jilaced upon a particidar bough of a paiticular 

 oak ill the preceding autumn! 



The third black oak, visited on May 21, 1865— which was 

 the smaU one— was absolutely loatled down with galls, and I 

 estimated their number at 50 or BO at least. At this early 

 period aU these galls were still small and immature, and it 

 was necessary to leave them for a week or two upon the tree 

 to riiii-n and mature . 



On June 5th, 1S65, I climbed the small gall-bearing black 

 oak, and stripped it of every gall that I could see. From it 

 I harvested only 18 normal spongifica galls, exclusive of 2 or 

 3 that had been destroyed by Icpidopterous larva;, and about 

 40 specimens of a particular form of gall (Q. pseudolincloHa:, 

 WaLsli) which occurs commonly but sparingly among tlie 



normal q. sponijifica gall.s, and also, in a slightly modified 



lip, iii,,,ii r,,,1 ,,,il,- inr,'- ir,l i,v 111,, Q m,,;,m'.s- gall. Foralong 



, ■; 11 lias been a great 



I,,, I ■ .■II ,1 ,, Mack oak orfi-om 



i.,i ,,.,! ::ii ii,.,i 'h 1 II M, ,• Ml. I ii,iii- iiiiinh-e.ls of them, and 

 liav.- U.pt tliiiii on han.i lor yi^ars, 1 have invariably bred 

 nothing from them but great numbers of a very large and 

 very handsome Chalds fly, belonging to the Pteromalidesyv\l\\ 

 concealed ovipositors, which 1 have never reared from any 

 other gall, and a few stray specimens of such Chalcis flics 

 (Caltimome and Eurytoma) as I have bred also from the nor- 

 mal Q. spongifica galls. My friend Baron Osten Sacken, to 

 whom I had bef.n-e this period communicated this peculiar 

 form of gall, suggested that it was a true Q. tpongifica gall, 

 modilieil by the action of the parasite that inhabited it; anil 



legative fact that 1 

 from it, after e> 

 > m three or four d 



ytbiiiKbnt 1 



in this ni 



dented conclusion. Th. ;.:ill n. ii ,,.ils0.sij 



inch in diameter, while the iioi ill I ,■ , jillolten 



attains a diameter of 1.75 inch, an. 1 i i,. ' .1, ih normal 

 .gall, except that it is often stml ; 1 li .sharji 



prickle-like tubercles similar to lliooi ..I lli<- . .\.jiui yallic- 

 linctoriic gall— whence the name that 1 have given it. The 

 central cell is round and about 0.20 inch iu diameter, with an 

 external crust which is only about 0.02 inch thick, instead of 

 forming a dense woody mass as in the normal form. The 

 external crust of the gall itself is similar to that of the nor- 

 mal gall ; but, instead of its being connected with the central 

 cell by homogeneous spongy matter, with a few subobsolete 

 slender radiating filaments among it, as in that gall, it is 

 connected with the central cell solely and exclusively by 

 dense, opaque, coarse, whitish cottony fibres, radiatiugfrom 

 the central cell, as in the Q. inanis gall, but differing widely 

 from those of that gall by being very much coarser, by being 

 cottony instead of smooth, and by being placed so close to- 

 gether as to occupy the whole space between the cell and the 

 external crust of the gall, instead of being separated from 

 each other by very wide interspaces. On my cutting into 24 

 galls that remained unbred from, on this 17th day of March, 

 1869, out of the above-meiitioiie.l lot of about 40 Q. pseudo- 

 tinctoria galls har^'este.l .Iim, im, i -;. .ij^-lit of them were 

 found to contain the .1 i i I m is imago already 



spoken of, seven what w I nuitiiic dead larva, 



one what was probably its ni mir. ,|. ,,1 pupa, one the pupal 

 shell of a 5 Caltimome, one a Eiinjloma sludiom 5 , Say, and 

 in six the tenant of the cell must have perished in early life, 

 for in these six the central cell was empty. 



On the supposition of the peculiar character of the Q. 

 pseudotinctorice gall being caused by the action of the large 

 Ptcromalidous parasite that generally, but not always, in- 

 habits it, and never inhabits the noinial tyjie of gall, it may 

 be asked how it happens that this v.i> ni, , . , . n '..tinctorice 

 gall sometimes produces the sam.- -p, , i , n i ,tUimome 



which is commonly bred from til.' _ ; u i .n .-asion- 



ally a Euri/Mmo, which is also bml .., i ;i-i M; iVoin the 



normal gall ? I can only suggest that, in these two latter 

 cases, the Caltimome and the Eurytoma are parasitic upon 

 the Large Pteroraalidous parasite, and that the peculiar char- 

 acter of the gall was determined in the first instance by the 

 Pteromalide. The Chalcidida: are, to a much greater extent 

 than is commonly supposed, secondary and not primary 

 parasites; and iu the case of the Jointr-worm J'ly (ftosoma 

 hordei, Harris) we have an instance of a Eury tomidous Chal- 

 cidian being preyed upon parasitically by three other Clial- 

 cidians— one a Torymua, a genus closely allied to Callimome, 

 and the other two belonging to the Pteromalides with short 

 ovijiositors. 



From the l.S normal Q. spongifica galls, obtained on .June 

 5th, 1805, as specified above, from the small black oak, I bred 

 on June 11th, 1805, one C. ?. spongifica q , and another ^ of 

 the same type on June 14th, 18C5. On cutting into the re- 



