784 SUMMAKY OF CUREENT RESEARCHES RELATING TO 



being unstained, appeared like vacuoles. Osmie acid and teasing 

 revealed the development of the spermatozoa. 



With regard to the nomenclatnre, Mr. Brown has, at the suggestion 

 of Prof. Lankester, avoided the use of such terms as spermatoblast, 

 and has substituted simple descriptive expressions. In the tubule 

 four layers of seminal elements are to be distinguished ; the most ex- 

 ternal consists of cells, the nuclei of which are all in the resting con- 

 dition ; of these nuclei there are three kinds, some belong to supporting, 

 some to growing, and some to spore-cells. In the second layer the 

 cells are large, and the nuclei all in a kinetic condition ; those of the 

 third layer are young spermatozoa ; and those of the fourth, spermatozoa 

 just ready to leave the tubule. 



The author describes the origin of the growing cells of the outer 

 layer from spore-cells, which divide in the first instance by a process 

 of budding, and subsequently the resulting cells undergo karyokinesis ; 

 the only writer who has given a somewhat similar account is Mr. A. B. 

 Lee, who has studied the spermatogenesis of Appendicularia ; the ex- 

 planation which he gives is regarded by Mr. Brown as accounting 

 very well for the process he has observed. The suggestion is that 

 the complex method of division by karyokinesis " is intended to 

 serve for the accurate division of the nucleus between the resulting 

 cells " ; the result of budding is to produce dissimilar cells, that of 

 karyokinesis is the production of growing cells precisely alike, which 

 again give origin to young spermatozoa which are again all alike. 



The author agrees with Swaen and Masquelin that, in the dog-fish 

 the spermatozoa are derived from primitive male ova, while the sup- 

 porting cells are derived from follicular cells, and he thinks it probable 

 that the same is the case with Mammals. 



Hatching of Birds' Eggs after Lesion of the Shell.* — Dr. L. 

 Gerlach has made experiments to show that the admission of a 

 diminished quantity of air to the blastoderm of the hen's egg, during 

 hatching, causes dwarfing of the embryo. He then tried whether an 

 increase in the size of the embryo could be obtained by increasing the 

 amount of air. 



In order to admit more air a part of the shell was scraped quite 

 thin. When this was done successfully (which rarely happened) and 

 the eggs were put in the incubator, no great increase of size was 

 apparent for the first two or three days, but after that there was a 

 remarkable increase in the rate of development. For example, an 

 embryo after 40 hours' incubation presented an appearance which is 

 generally only visible at the end of the third or in the course of the 

 fourth day. 



A second method of admitting more air was to remove whole 

 pieces of the shell, great care being taken so as not to injure the shell 

 membrane or blastoderm. 



The fracture must be at some distance from the blastoderm so 

 that the desiccation which ensues on this removal of the outer cover- 

 ing shall not extend to the embryo. These precautions being observed 



* SB. Physikal.-Med. Soc. Erlangen, 1884, p. 129. 



