102 CARNEGIE INSTITUTION OF WASHINGTON. 



and Mall, as follows: First month, embryo length from to 2.5 mm.; 

 second month, 2.6 to 25 mm.; third month, 26 to 68 mm.; fourth 

 month, 69 to 121 mm. ; fifth month, 122 to 167 mm. ; sixth month, 168 to 

 210 mm.; seventh month, 211 to 245 mm.; eighth month, 246 to 284 mm.; 

 ninth month, 285 to 316 mm.; tenth month, 317 to 336 mm. or larger. 

 In addition to various papers which have appeared from time to 

 time during the past year, and which are Hsted in this volume (see 

 BibHography, pages 36-46), the following have been published by 

 the Carnegie Institution or are in course of publication : 



Publication No. 224: 



No. 10. Mall, Franklin P. The human magma reticule in normal and in pathological 



development. 

 No. 11. Cowdrjs E. V. The structure of chromophile cells of the nervous system. 

 No. 12. Cunningham, R. S. On the development of the lymphatics of the lungs in 



the embryo pig. 

 No. 13. MackUn, Charles C. Binucleate cells in tissue cultures. 

 Publication No. 225: 



No. 14. Weed, Lewis H. Development of the cerebro-spinal spaces. 

 Publication No. 226: 



No. 15. Mall, Franklin P. Cyclopia in the human embryo. 



No. 16. Thm-low, Madge D. Quantitative studies on mitochondria in nerve cells. 



No. 17. Lewis, Margaret Reed. The development of connective-tissue fibers in tissue 



cultures of chick embryos. 

 No. 18. Sabin, Florence R. Origin and development of the primitive vessels of the 



chick and of the pig. 

 No. 19. Johnson, Franklin Paradise. A human embryo of twenty-four pairs of 



somites. 

 Publication No. 227 (in press) : 



No. 20. Streeter, George L. The histogenesis and growth of the otic capsule and its 



contained periotic-tissue spaces in the human embryo. 

 No. 21. 'Wheeler, Theodora. Study of a human spina bifida monster with encephal- 



oceles and other abnormalities. 

 No. 22. Van der Stricht, O. The genesis and structure of the membrana tectoria 



and the crista spiralis of the cochlea. 

 No. 23. Ingalls, N. W. A human embryo before the appearance of the myotome. 



As a sixth contribution on the pathology of human embryos I have 

 published a study on Cyclopia, as one of the papers in Publication 

 No. 226 of the Carnegie Institution of Washington. In this connection 

 it may be of interest to mention that the progress made during recent 

 years in the study of teratology has been so marked that it is now 

 possible to reconsider the whole subject and to place it upon a perma- 

 nent scientific basis. For this progress we are indebted almost entirely 

 to the experimental embrj^ologists. Problems which formerly seemed 

 impossible of solution — for instance, the formation of double monsters — ■ 

 have yielded as if by magic to the embryologist who made experi- 

 mental studies upon the lii-ing egg. Perhaps the best example that 

 can be brought forward to illustrate this point is the question of the 

 cause of cyclopia. As soon as it was possible to experiment upon eggs 

 in such a way that practically all of them developed into cyclopean 

 monsters, the explanation of this condition was at hand. No impor- 

 tant organ develops from the midline of the medullary plate, and this, 



