338 ABSTRACTS OF PAPERS. [VOL. II. 



6. No Stegocephalan as yet known can have served as ances- 

 tor of Urodeles, Annra, or Caecilians. The parent form must 

 have possessed characters intermediate between the known 

 Stegoccphali and the Crossopterygian ganoids. 



7. The ancestry of the Amphibia must be sought in the 

 Crossopterygii and not in the Dipnoi. 



8. The balancer of the Urodele larva is a modified external 

 gill belonging to the hyoid arch. 



IX. PHAGOCYTOSIS IN A MAMMALIAN OVARY. 



MAYNARD M. METCALF. 



IT has long been known that in the ovaries of certain Mam- 

 mals and Fishes syncytia of young ova are found, and that of 

 the several nuclei in such a syncytium one or but few persist 

 as nuclei of definitive ova. Apparently, in these cases, the cells 

 which disappear are used as food for the persistent ova. 



In the ovary of the common Cat somewhat similar conditions 

 have been observed by the author. Many of the young ova, in 

 the stage when they are surrounded by a follicle consisting of 

 but two layers of cells, are seen to have ingested many of the 

 follicle cells, and the nuclei of these ingested cells can clearly 

 be seen, some quite perfect (newly ingested), others apparently 

 in different stages of digestion. The nuclei of these ingested 

 cells, when almost completely digested, appear as groups of 

 granules, these granules being apparently the remnants of the 

 nodal thickenings of the chromatin network of the ingested 

 cells. Such an ovum with its ingested nuclei very closely 

 resembles the young blastomeres of a Salpa embryo, which 

 have the same habit of devouring follicle cells. 



Many young ova with ingested follicle cells were found in 

 one Rat ovary. In another ovary of a White Rat no ingestion 

 of follicle cells was found, nor was ingestion found in the ovary 

 of a Gray Squirrel examined. Pressure of other duties has 

 prevented the author from determining if such ingestion of 

 follicle cells be normal in the ova of Rats and, if so, what 



