4174 Linnean Society. 



from trout, in wnich the latter gentleman had succeeded. After pressing the subject 

 on the attention of all who may have the opportunity of making experiments, Mr. 

 Fisher concludes his letter by a caution against what he considers an incorrect state- 

 ment, taken from the Perth Courier, in which it is said that Dr. Robertson, of Dun- 

 keld, "conceiving that the ova of the female were impregnated previous to their deve- 

 lopment, within the body of the fish," had taken " a number of live female trout from 

 the spawning-bed, and having extracted the roe, deposited them in a perforated zinc 

 box, containing also some gravel," which was " upon the 14th of October last, placed 

 in a running stream, and on examining the box [in April], several of the ova were 

 found to be hatched." On this latter experiment, Mr. Hogg observed, that the 

 result could only be accounted for by one of the two following methods. Either 

 the ova of the female trout had in some way received the influence of the fecundat- 

 ing principle of the male trout, previous to Dr. Robertson's depositing them in his 

 perforated zinc box ; or, the perforated zinc box, which contained the ova as ex- 

 pressed from the females, was placed in the running stream within the fecundat- 

 ing influence of the males. The former solution he founds on the mode of spawning 

 described by Mr. Ellis in his 'Natural History of the Salmon,' from which it would 

 appear that the male and female fishes having jointly made a furrow in the gravel, 

 place themselves one on each side of it, and throwing themselves upon their sides, 

 " again come together, and rubbing against each other, both shed their spawn into 

 the furrow at the same time. This process is not completed at once ; it requires 

 from eight to twelve days for them to lay all their spawn. *' Mr. Hogg argues from 

 this description, that it is possible that the female trout from which Dr. Robertson 

 took the ova might have gone through this process with the male, and might have 

 thus received the fecundating influence just before she was caught ; but on this solu- 

 tion he does not rely. He thinks it more probable that in the running stream in which 

 the perforated zinc box was placed, there were some male trouts which had deposited 

 their milt near the box, and that some of the milt might have been carried with the 

 stream through the holes of the box, and have so fecundated the ova within it. In con- 

 elusion, he suggested, that as doubts still exist as to the processes which the male and 

 female salmon and trouts naturally adopt at the spawning season, experiments on the 

 subject might readily be undertaken, by confining them, at the proper seasons, in large 

 glass cases or tanks, covered over with a coarse wire gauze, such as those which have 

 recently been constructed in the water-vivary of the Zoological Gardens. A stream 

 of fresh water, regulated by pipes, could easily be supplied in all districts where the 

 salmon tribe abounds. 



Dipterous Parasites of the Earwig. 

 Read also, " Notes on the Dipterous Parasites which attack the common Earwig 

 and the Emperor Moth." By George Newport, Esq., F.R.S., F.L.S., &c. After re- 

 marking that it is well known to naturalists that many Dipterous insects of the family 

 Tachiuarhe infest the Lepidoptera, Hymenoptera, and Coleoptera, Mr. Newport stated 

 that he has recently found one of the Dermaptera, also the common earwig, to be sub- 

 ject to the attacks of a species of the same family. He has obtained this parasite, 

 both in its larva and pupa state, from earwigs collected in the autumn in the neigh- 

 bourhood of London. The earwig is attacked during its larva, or in the earlier period 

 of its pupa state, when the covering of its body is soft and easily perforated. The fly 

 then attaches a single egg to some part of its surface, and the young parasite hatched 



