48 SUMMARY OF CURRENT RESEARCHES RELATma TO 



terminate in a filamentous process, wliich enters into connection witli 

 the similar filaments of the neighbouring tubes. 



The tubes are camerated internally, and this cameration is obvious 

 from without owing to the contraction of the outer walls ; the wall of 

 the tubes is formed by a distinct unilaminate epithelial layer ; like 

 Brass, the author was unable to detect any tunica propria ; in the region 

 of the oviduct the epithelial is invested by a muscular layer. At the 

 other end, the terminal chamber of a mature ovary consists of two 

 closely connected parts ; in the inner one there is a homogeneous 

 mass of protoplasm and then a number of cellular elements which 

 fill up the space between the central protoplasm and the investing 

 epithelium ; both in position and structure these cells present the 

 same appearance and relations as the yolk-forming or nutrient cells 

 of oviparous Aphides ; the central protoplasmic mass which they 

 surround may be spoken of as the rachis. Like the young egg, these 

 cells are without a membrane. 



In the lower portions of the ovarian duct the flattened are 

 replaced by cylindrical epithelial cells, and here large cells, which are 

 young ova, are to be detected ; the resemblances between these and 

 the ova of oviparous forms is insisted on ; we may indeed sum up the 

 matter in saying the egg is attached to the central rachis by a stalk. 

 The characters of the ova in succeeding chambers are pointed out, and 

 attention is given to the fact that every two chambers are separated by 

 a layer of cells formed by a thickening of the epithelium, and that 

 there is in the centre only space sufficient for the passage of the 

 connecting cord. 



The function of the ovarian stalk is discussed, and the result is 

 come to that the ova grow by their own power of assimilation as well 

 as in consequence of the assimilative power of the stalked rudiments ; 

 it seems to be clear that there is a streaming of the protoplasm which 

 passes from the young ova through their stalk into the rachis and 

 then through the cord of connection to the egg ; it follows from this 

 that the stalked cells of the terminal chamber must be regarded as 

 rudimentary ova ; they are not as Ludwig thought, nutrient cells, but 

 true " Eianlage." 



The author next passes to an account of the formation of the 

 blastoderm, and he finds that in the viviparous Aphides the germinal 

 vesicle does not disappear, but is directly converted into the first 

 cleavage-nucleus. The first two spheres are only incompletely 

 separated from one another; after this, fissive processes take place 

 with great rapidity, and there appear to be no stages of repose. 

 While the earlier divisions are being effected the egg increases 

 greatly in size, and gradually becomes altered in form, exchanging its 

 spherical for an elongated appearance. 



The views and accounts of Brandt, Leuckart, and Brass are 

 carefully reviewed. 



Chlorophyll in Aphides.* — L. Macchiati having noticed that 

 certain Aphides when placed in a dark situation lost their colour in 



* Bull. Soc. Entomol. Ital., 1883, pp. 163-4. 



