ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 575 



which invests the ray, and which is homogeneous, is not, in Banatra, formed 

 within the double cells, but is secreted by the neighbouring cells in the form 

 of a cuticle ; and we have, therefore, the somewhat remarkable phenomena 

 of the union of a rare form of intracellular chitin formation with the ordinary 

 or typical form of cuticular secretion of chitin. The observation of the 

 whole process of chitinization leads the author to the belief that it is due 

 to the direct influence of the nuclei on the activity f)f the cell. Although 

 the substance given off by the nutrient and the double cells is so different 

 in nature, yet it is impossible to dispute the similarity of the two processes. In 

 both kinds of cells, i.e. in the nutrient cells of Lepidoptera and the double cells 

 of Nepa and Banatra, the nucleus extends in the form of amceboid processes 

 through the cell ; and as in both cases a substance is excreted by the cell, 

 it is very probable that the nucleus thus increases its surface for the pur- 

 pose of increasing the constant action between the nuclear and the cell- 

 substance. It thus exerts a greater influence on the secretory activity of 

 the cell. 



The second chapter deals with the exit of the ovum from the ovary, and 

 the fate of the empty ovarian follicle ; and with the relation of the egg- 

 forming organ to the efferent apparatus. The result of the investigation 

 of a number of forms is this : the ova always make their exit from the 

 ovarian tube in one typical way, which, however, presents a number of 

 variations due to the characters of the ovarian chamber after repeated 

 ovipositions ; the variations may be ascribed to the variations in the form 

 of the ovarian tube, and to the characters of its epithelium. In all cases 

 the egg-chamber is broken through at its base, since here there is always a 

 cellular partition, which opposes the passage of the ova from the ovary into 

 the efferent apparatus ; the injury suffered by the tube varies considerably. 

 Sometimes there is not only fissure, but an extension of the constriction at 

 the base of the tube, when the egg passes from the tube into the duct 

 without the connection between the two being broken. In other cases, 

 however, when the epithelium of the ovarian chamber forms a very thin 

 layer, the exit of the ova is accompanied by a destruction of the epithelium, 

 and the consequent breaking up of the whole chamber, of which the tunica 

 propria alone remains ; here, of course, the connection between the ovi- 

 gerous and the oviducal organs is suddenly broken ; it is more marked when 

 the constriction between the separate egg-chambers has gone so far, that 

 they are only connected by a thin filamentary piece, for here it is impos- 

 sible for the ova to pass on ; the ovigerous and oviducal portions may in 

 these cases be connected by nothing but the surrounding peritoneal in- 

 vestment ; the walls of the emptied egg- chamber fall together, and form 

 isolated balls of cellular substance, until they are absorbed. "We have here, 

 it is obvious, to do with a very interesting phenomenon ; the true ovary as 

 represented by the oviducal tube is, by a normal act of destruction, 

 separated from the rest of the generative apparatus ; in certain cases the 

 ovary again becomes connected with the efferent apparatus, and the 

 solution and reparation of continuity is periodically effected. 



In the third chapter, Dr. Korschelt deals with abnormal processes in 

 the development of insects' eggs. In Beduvius personatus and Bomhus 

 lapidarius the lowest ovarian chamber has its wall considerably thickened, 

 as if in consequence of the thickening of the epithelial cells ; and the 

 chamber seems at first to have been emptied and to be undergoing retrograde 

 change ; closer examination, however, shows that we have to do with a 

 chamber which still contains ovarian rudiments, although altered in 

 condition. 



In Beduvius personatus the lowest ovarian follicles of some of the tubes 



