DEPARTMENT OF EMBRYOLOGY. 91 



apparent that the hypothesis of Hensen, that rupture is induced solely through 



increased arterial tension, is incorrect. Repeated experiments with mature 



follicles, in which injections of the ovarian and uterine arteries were made 



under great pressure, failed to result in a single instance of rupture of the 



follicle. 



ANOMALIES IN DEVELOPMENT. 



Zygodactyly and its Inheritance. 



The occurrence of anomalous webbing between the toes has been studied 

 by Dr. A. H. Schultz with reference to its embryology and its relation to 

 heredity. He finds that it is normally present in early development and that 

 in the rare cases where it persists it is to be Regarded as a developmental 

 arrest. Where it shows a familial incidence, it does not skip a generation. 

 The cases thus far reported indicate that the chance for the female to trans- 

 mit webbed toes is very much less than for the male, and furthermore, female 

 progeny is less apt to inherit the condition than male progeny. It is of in- 

 terest to note that zygodactyly of the foot seems always to occur between the 

 second and third toes. The condition in mammals is not restricted to man; 

 it is found in several groups of marsupials and in the siamangs (apes from 

 Sumatra and the Malay Peninsula). In these animals skin fusion between 

 the second and third toes is a constant occurrence. When the fusion is present 

 in man the tendon of the long extensor muscle for toes II and III is unsplit 

 for an unusually long distance. 



Bregmatic Fontanelle Bones. 

 Special interest attaches to the bregmatic bones for the reason that in a 

 few mammals they seem to be almost the rule, while in a large majority of 

 mammalian skulls their occurrence is exceedingly rare and in some they have 

 never been found. Through the cooperation of the National Museum at 

 Washington and the American Museum in New York, Dr. Schultz has been 

 able to supplement his own material and thereby carry out a study of varia- 

 tions in number, size, and shape of these but little-understood bones in dif- 

 ferent mammals. It would appear that they are to be regarded as a new 

 acquisition in mammals, in which here and there the normal skull bones prove 

 insufficient to close the fontanelle in due time. Any theory regarding the 

 bregmatic bones, however, must await substantiation until our knowledge 

 of the factors involved in the normal closure of the great fontanelle in mammals 

 has been lifted from its present rudimentary state. 



GENERAL. 



During the past year, from July 1, 1921, to June 30, 1922, there were 589 

 accessions to our collection of human embryos. Among them are some very 

 valuable young specimens which will serve to fill some of the gaps existing 

 among our early stages. At the present time, owing to the limitations of our 

 storage facilities, we are not able to preserve all the material received. How- 

 ever, measurements and records are kept of all specimens for the purposes of 

 statistical studies. A certain amount of relief from our cramped condition has 

 been secured for the coming year through the courtesy of the Johns Hopkins 

 Medical School, which has placed at our disposal four rooms in the Hunterian 

 Building on the floor below the one in which we are now located. This will 

 not only provide additional storage room, but will also give us two research 

 rooms which are needed for visiting investigators. 



