538 SUMMARY OF CURRENT RESEARCHES RELATING TO 



from this in the form of nascent endoplasm. It would appear, there- 

 fore, that nutritive material ingested by the cytoplasm receives its final 

 elaboration in the nucleus. The nascent endoplasm has probably the 

 greatest activity, while the functions of the ectoplasm are more passive 

 and mainly in the direction of maintaining structural continuity between 

 neighbouring cell-elements. G. The ectoplasm corresponds to the so- 

 called intercellular substance, and forms an essential part of the con- 

 tinuous living tissue which with its contained nuclei constitutes a 

 Plasmodium. 



Tissues of the Ovary in Marsupialia.* — C. PI. O'Donoghue has 

 investigated the corpora lutea and the interstitial tissue in the ovary in 

 Marsupials. For this study he used chiefly three forms : PliascoJarcios 

 cinereus,- Trichosurus vulpecuJa, and Didelpliys cmrita, but other species 

 were used for purposes of comparison. He finds that the membrana 

 granulosa in the three species studied is composed of typical polygonal 

 cells arranged three or four cells deep round the ripe follicle. The 

 theca foUiculi is composed of internal and external layers, does not 

 contain any included interstitial cells, and its cells are always readily 

 distinguishable from membrana granulosa cells. The corpus luteum 

 in P. cinereus is formed by the irruption of both layers of the theca 

 folliculi, which burst through the membrana granulosa and form a 

 lining on its inner side. This method of formation is similar to that 

 in F. obesuJa, P. nasvfa, and 3f. riificoIUs. The ripe follicle collapses 

 in T. vulpecula when the ovum is extruded, and the central cavity is 

 at once obliterated. The theca folliculi is drawn in with the membrana 

 granulosa, which it penetrates, and the connective tissue becomes 

 irregularly distributed through the body. It is unlike the process in 

 any other Marsupial so far examined, but to a certain extent resembles 

 that in the mouse. In D. aurita the thecal irruptions do not at once 

 go through the membrana granulosa, but push it before them until the 

 central cavity is practically filled in, and then they break through and 

 form the central plug of connective tissue. In one example, a very 

 early stage, mitoses were found in the cells of the membrana granulosa, 

 and this was the case also in P. obesula and P. nasuta. The corpus 

 luteum in P. cinereus remains hollow even when fully grown, and the 

 central cavity does not get filled in till after the birth of the young, 

 apparently not until the gland has started to decline. This condition 

 is apparently unique. In T. vulpecula the corpus luteum is fairly 

 typical when full-grown, save that its connective tissue is much more 

 irregularly arranged than in other Marsupials. The condition of the 

 corpus in D. aurita is very similar to that in D. viverrinus. In no case 

 is the membrana granulosa shed, nor does the theca interna contribute 

 to the lutein cells of the corpus luteum. 



The interstitial tissue. There is present in the ovary of certain species 

 of Marsupials a tissue which corresponds histologically to the interstitial 

 tissue in the ovary of the higher Mammals. The cells are always 

 distinguishable from ordinary stroma cells, cells of the theca interna,. 



* Quart. Journ. Micr. Sci., Ixi. (1916) pp. 433-73 (1 pi.). 



