RECORDS OF MEETINGS 277 



both the bird and the mammal the development of the thoracic ■ duct 

 becomes complicated by a direct or indirect relation of the lymphatic 

 anlages to the adjacent elements of the hasmal (venous) vascular system^ 

 In the bird the relation of the lymphatic anlages to the ha^mopoetio 

 axial mesenchyme is direct, the avian thoracic ducts becoming for a time 

 functionally Jimmoplioric. 



In the mammalian embryo the relation of the developing thoracic ducts- 

 to the axial venous system is indirect, 'the lymphatic anlages replacing 

 the temporary ventro-medial hsemophoric azygos tributaries topograph- 

 ically, but never themselves assuming the ha^mophoric function. 



In all three classes of amniote embryos the final results of the genetic 

 processes outlined above is the same, viz., the establishment of a peri- 

 aortic, or para-aortic, lymphatic channel, the amniote thoracic duct. In. 

 a wider interpretation it becomes evident that all the diversified phenom- 

 ena of vascular ontogeny, hsemal as well as lymphatic, are focussed in 

 the small field which any extra-embryonic vascular area presents. 



The Section then adjourned. 



W. K. Gkegory, 



Secretary. 



SECTION OF GEOLOGY AND MINERALOGY 



15 May, 1916 



Section met at 8:15 p. m., Vice-President Douglas W. Johnson pre- 

 siding. 



The minutes of the last meeting were read and approved. 

 The following program was presented : 



H. E. Anthony, Peeliminary Eepoet on Fossil Mammals op 



Porto Eico. (Read by Title.) 



E. T. Hodge, Geology of the Coamo-Guayama Region, Porto 



Rico. 



D. R. Semmes, Geology of the San Juan District, Porto Rico, 



Chester A. Reeds, Fossil Faunas of Porto Rico. 



Charles P. Berkey, Plans for Field work in Porto Rico during 

 1916. 



Summary of Papers 



Mr. Hodge stated that the Coamo-Guayama district is located in the 

 east central portion of southern Porto Rico. The rocks of this area are 



