364 Transactions of the Canadian Institute [vol. ix 



intestinal tract throughout, and that therefore if Kerner's theory be 

 correct frass should be found as in the sawfly galls. 



Further evidence in favor of Kiistenmacher's view is furnished by 

 a comparison of the stomach contents of a Cynipid and an inquiline 

 larva. The former consists of a mass of extremely fine particles, among 

 which can be detected nothing that is recognizable as having formed a 

 part of a cell (Fig. 55). As this material passes along the digestive tract 

 it becomes less dense the nearer it is to the posterior opening, and is en-, 

 tirely absent in the last part of the canal (Figs. 61, 62). The latter con- 

 sists of much coarser material in which crystals, similar to those in the 

 surrounding cells, and parts of cell walls can be easily detected. These 

 contents are shown in Fig. 56, and at a higher magnification in Fig, 57. 

 So characteristic is this difference between these two classes of stomach 

 contents that by means of it alone a Cynipid can be easily distinguished 

 from an inquiline larva. 



The data already presented furnish indirect proof that only the 

 contents of the cells form the food of the Cynipid larva. An examination 

 of the walls of the cells immediately surrounding the larva gives direct 

 evidence in favour of this hypothesis. The nutritive layers of a large 

 number of Cynipid galls were examined at different stages of development, 

 and in none of the examples did the walls of the cells appear to have been 

 eaten a^vay by the larva. A layer of collapsed tissue (Figs. 52, 59, 60), 

 especially in the older specimens, is often found around the inside of the 

 larval chamber and there are also many empty cells throughout the 

 nutritive zone. These are shown in the inner row of cells in Figs. 59, 60. 

 In some cases the radial walls of the cells are wrinkled, indicating that 

 these cells are gradually contracting. This can be seen with the aid of a 

 lens in Fig. 59. The folds are not found in the tangential walls of the 

 cells. The majority of the empty cells are found in the row that lines 

 the interior of the larval chamber (Fig. 60), but others are distributed 

 irregularly throughout the entire nutritive zone. These can be seen in 

 Figs. 59, 60. There does not seem to be the slightest possibility of doubt 

 that the larva withdraws the contents from the cells of the nutritive zone 

 without dest oying the walls, and that inconsequence the cells surrounding 

 the larva gradually collapse. 



If an inquiline larva is feeding in the gall, a ragged, broken edge of 

 tissue is found lining the cavity in which it is living, a marked contrast 

 to the smooth interior of the Cynipid larval chamber. This uneven 

 edge is shown in Fig. 56, compare with Fig. 55. Neither of these views 

 takes into account the possibility of enzyme action in rendering more 

 soluble the contents of the nutritive zone. 



