30 The Scottish Naturalist. 



the superficies of a leaf in the same manner as Spathegaster. I 

 think this admirable discovery is of the greatest importance for 

 further observations. If we find again a species with an oviposi- 

 tor not fit to make the galls of the species, we are justified in pre- 

 suming a similar alternating generation with some other species. 



'' The difficult question how the eggs of Cynips are able to 

 pass through the comparatively small ovipositor, is described 

 with much detail and acumen. The observation was only 

 possible by the ingenious device of chloroforming the insects 

 in the act of oviposition, and making an anatomical investigation 

 of the parts. By repeating the observation many times in 

 different stages of the act, a full series of observations, one 

 completing the other, gav^e a clear and satisfactory result, and at 

 the same time the place was ascertained in which the egg was 

 laid. A large number of other interesting details concerning the 

 formation, structure, and the growth of the galls, are given, which 

 must be studied in the original paper. I may only add the sur- 

 prising fact of the continuous rotation of the embryo in the ^gg, 

 till it is hatched. The rotation is not made as in molluscs, by 

 vibrating cells, but by the alternate contraction of long spindle- 

 shaped cells, which are attached to the hypodermis. 



" Similar experiments with similar results followed also through 

 the whole cycles, proved that Ncurotenis lenticidaris is the winter 

 form of Spathegaster baccarum, and N. nuviismatis the winter 

 form of Sp. vesicatrix. Dr Adler adds that experiments with all 

 three species are not very difficult, and he believes that every 

 student will be able to repeat them. 



" It seemed to the author more than probable that such 

 alternating generation would not exist alone in Neuroterus. 

 Similar observations and experiments followed through all the 

 cycles proved that Dryophanta sciitellaris is the winter form of 

 Trigonaspis cnistalis, and Dryopha7ita longiventris the winter 

 form of Spathegaster Taschenbe?'gi ; but for the last species only 

 half the cycles was till now ascertained. 



" Direct observations proved that the egg of Dryophanta is 

 laid with the egg-body downwards and the stem of the egg 

 upwards. The situation is just rtversed \n Neuroteri/s : and as 

 the egg is always hatched through the hind portion, the larva 

 of Dryophanta is obliged to make its galls downwards in the 

 cambium, and the larva of Neuroterus upwards on the leaves. 



" Another agamous genus, Aphilothrix, possesses an ovipositor 

 similar to Neuroterus^ and it seemed impossible that the large 



