EMBRYOLOGICAL RESEARCH. 291 



Weed on the nuclear masses in the lower part of the human medulla, 

 which will be published by the Carnegie Institution of Washington; 

 a critical review of recent work on the development of the lymphatic 

 system, by Professor Florence R. Sabin, to be published in the Ergeb- 

 nisse fur Anat. u. Entwickl.; a chapter on the development of the 

 ventral abdominal wall in a book on the umbilicus by Professor T. S. 

 CuUen, to appear shortly; an article by Dr. Ernest K. Cullen and 

 myself on an ovarian pregnancy located in a Graafian follicle, in Sur- 

 gery, Gynecology and Obstetrics ; and an article on the development 

 of the structural unit of the pancreas by Dr. George W. Corner, for 

 the American Journal of Anatomy. 



During the spring and summer research in human embryology was 

 pushed with increased vigor. A study of tubal pregnancy, which 

 includes nearly 100 specimens, is drawing to a close. An effort has 

 also been made to establish the norm for the external form of human 

 embryos less than 25 mm. long. At present it is possible to recognize 

 14 distinct stages in embryos less than an inch long, and this provisional 

 classification will be perfected as more specimens are recorded either 

 here or elsewhere. At the same time uninterrupted work has been 

 given to the study of the anatomy of the human embryo. This work, 

 hitherto in a fragmentary state, and depending on the chance activi- 

 ties of various investigators, can now be pursued in a systematic way. 

 A laboratory of human embryology should be peculiarly fitted to do 

 this. Such an effort, free from the fortuitous character of experi- 

 ment, may constitute an important part of the routine activity of the 

 department. In addition to the development of specific tissues or 

 organs, monographs should be issued on the structure of the embryo 

 at representative stages. The Institution has already made it pos- 

 sible to complete the work of Professor Lewis on the development of 

 the head with special reference to the muscular system, which has 

 occupied him for a number of years. Studies of young embryos are 

 represented by the records and reconstructions which Professor 

 Evans has been assembling on the anatomy of human embryos 

 between 2 mm. and 4 mm. in length. A satisfactory presentation of 

 the complex anatomy of older stages has also been begun in the 

 detailed study of an unusually well-preserved injected embryo 21 

 mm. long (No. 460 of the collection). Sections of the embryo are 

 being photographed at 50 diameters with microplanar lens, draw- 

 ings having already been secured of the surface form. 



A colony of guinea-pigs has been secured for breeding purposes, 

 and compartment cages built so that individual records will be pos- 

 sible. At present experiments are being made on the behavior of the 

 placenta toward vital stains, but valuable embryological material 

 will also be obtained from the colony. 



