CONTENTS 



No. 1. DECEMBER, 1919 



George T. Hargitt. Germ cells of coelenterates. VI. General considerations, 



discussion, conclusions. Thirty figures (three plates) 1 



Carl L. Hubbs. A comparative study of the bones forming the opercular 

 series of fishes 61 



George Orihay Shinji. Embryology of coccids, with especial reference to the 

 formation of the ovar}^ origin and differentiation of the germ cells, germ 

 layers, rudiments of the midgut, and the intracellular symbiotic organism. 

 One hundred thirty-three figures (twenty plates) 73 



Charles L. Parmenter. Chromosome number and pairs in the somatic 

 mitoses of Ambystoma tigrinum. Thirty-seven figures (nine plates) 169 



No. 2. MARCH, 1920 



Hachiro Yuasa. The anatomy of the head and mouth-parts of Orthoptera and 

 Euplexoptera. One hundred and sixty-three figures (nine plates) 251 



Wm. a. Kepner and Frank Helvestine, Jr. Pharynx of Microstoma cauda- 



tum. One text figure and three plates 309 



H. D. Reed. The morphology of the sound-transmitting apparatus in caudate 

 Amphibia and its phylogenetic significance. Eighteen text figures and six 

 plates 325 



George W. Tannreuther. The development of Asplanchnia ebbesbornii 



(Rotifer). Twenty-one text figures and seven plates .389 



Tracy, Henry C. The clupeoid cranium in its relation to the swimbladder 

 diverticulum and the membranous labyrinth. Three figures and four 

 plates 439 



O. W. Hyman. The development of Gelasimus after hatching. Twelve olates 



(eightj^-eight figures) 485 



Louise Smith. The hj'-obranchial apparatus of Spelerpes bislineatus. P'ifteen 



plates (forty-seven figures) 527 



