affecting the Potato-crops. 113 



detailed. It appears that M. Rayer has discovered a similar 

 species which breeds in muUitudes in rotten potatoes ; and the 

 same animals were observed by Mr. Graham and myself last 

 March, in myriads in the putrescent tubers. This Vibrio is named 

 by Guerin, Rliabditis tuherculorum, and is shorter and stouter in 

 its young state : the tail of the male is rounded ; conical and 

 pointed in the female : the mouth is furnished with 2 rounded 

 nipples, and a 3rd between them connected with the oesophagus, 

 and the body is devoid of articulations (fig. 63, magnifiedj : it is 

 not thicker than the finest hair, and scarcely visible in repose. 

 As it is well figured, with dissections, in the Bulletin so often re- 

 ferred to in this Report, it is unnecessary to comment further 

 upon this worm at present. 



I am not aware that snails injure the potato-crops at any period, 

 but slugs do much mischief to the late crops, enlarging the holes 

 perforated by wireworms, snake millipedes, and other subter- 

 ranean animals, which is one good reason for lifting the crop as 

 soon as the tubers are ripe, to prevent unnecessary waste. This 

 reminds me of a singular fact recorded in a useful monthly pub- 

 lication called the ' Farmers' Herald.'* A bag was found in a 

 cooked potato, containing 1 1 white globular pellucid eggs, 

 scarcely so large as mustard-seeds : they were a little pointed at 

 one end, and had every appearance of having been laid in the 

 cavity by a slug, which is exceedingly probable, as I have found 

 them half concealed in potatoes, where they had feasted so long 

 and increased so greatly in bulk, that it was impossible to with- 

 draw them without enlarging the orifice. 



I believe this may close my observations regarding the insects 

 and small animals which directly or indirectly injure the potato- 

 crops. They amount to 60 er more, but probably their name 

 would be ' Legion ' if we were thoroughly acquainted with all 

 the species, in their different stages of development, preying upon 

 this useful esculent; and although in the foregoing pages no 

 attempt has been made to give undue importance to their agency, 

 there can be no question that insects often injure the potato- 

 crops to a great amount. Indeed, as we have endeavoured to 

 show in these Essays, their mission is to labour in the destruction 

 of vegetable and animal matter, and consequently there is not a 

 crop in the field and garden that, sooner or later, is not subject 

 to their ravages. 



A Summary of the present Essay. 



Aphis of potato, the same as that on the turnip, named A. 

 Rapce, and identical with A. vastator. 



Various species of Aphides are found upon potato-haulm, as 



VOL. X. I 



