ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 423 



Suitable objects for study are to be found in the Neuroptera, e. g. 

 ^schna or Agrion, where the ovigerous sheaths are very long, and 

 contain but a limited number of cells. The presence of vitellogenous 

 cells makes no difterence to the history of the epitheliiun, but the 

 ovule is more complex ; the indifferent cells of the ovariole, instead 

 of being directly transformed into the ovule, proliferate, and give 

 rise endogenously to a number of cells ; this number is constant for 

 the species, and even for a more or less large group. This may be 

 easily seen in the Lepidoptera ; but even here the mother-cell does 

 not expel young cells, but they become free in the ordinary manner. 

 In this group also M. Perez denies the accuracy of Prof. Sabatier's 

 observations. 



M. A. Sabatier* answers the criticisms of M, Perez. He urges 

 that the latter's opinion that the follicular cells are primitively 

 identical with those of the primitive ovules cannot be sustained, when 

 it is known that the former are at first very much smaller than the 

 latter ; a study of the ovary of Musca or of Acridium is sufficient to 

 demonstrate tlae exactness of this observation. Similarly as to the 

 origin of the nutritive cells, M. Sabatier states that in Dytiscus a finely 

 granular vesicle was seen to form in the yolk of the egg, which was 

 identical with the nuclei of the nutritive cells : in spiders and some 

 other forms similar intervitelline nuclei are developed, and they 

 only diiler in being absorbed by the egg before instead of after 

 expulsion. 



From his observations on the morphology of the ovary of insects, 

 M. Sabatier concludes that the nutritive, like the follicular cells, are 

 elements eliminated from the egg, that they only differ in size and 

 in the time of their appearance, and that there is no reason for 

 establishing an essential difference between insects which have only 

 follicular cells, and those which have also nutritive cells. 



In a further note on the elements contained in the ovigerous 

 sheath of Insects f M. Perez contends that the filament in which 

 the ovigerous sheath frequently terminates, is only the atrophied 

 portion of the sheath primitively filled with cells up to its blind ex- 

 tremity. The elements described by M. Sabatier in this region, are 

 neither ova nor follicular cells. It is only in the ovariole itself, 

 whether it reach the blind end of the sheath or be more or less 

 removed from it, that ova, follicular cells, and so-called " nutritive 

 cells " are found. 



The author considers M. Sabatier's description of the formation 

 of the two last sets of cells from the ovum, as perfectly erroneous. 

 He considers it quite impossible to count the number of " nutritive 

 cells " by means of sections. He treats them in the following way : 

 the ovariole is spread out beneath a lens; it is then cut so as to 

 separate an ovum with the surrounding cells from the ovariole ; by 

 pressing this portion the cells are set free ; the preparation is stained 

 and the cells counted. In this way the author finds three of these 

 cells in Panorpa, seven in Lepidoptera, fifteen in Diptera, sixty-three 

 in the bee. The " nutritive cells " described by Sabatier as being 



* Comptes Kendus, cii. (188(3) pp. 441-3. t Ibid., pp. 557-9. 



