1904.] NATURAL SCIENCES OF PHILADELPHIA. 691 



setts, during the summer months by Verrill (1895) and by Miss Moore 

 (1899), so that it would appear that some few individuals lived over 

 the summer. 



The animals found in the aquaria were probably imported on sea- 

 weed gathered at Wood's Hole, Massachusetts, or at Sea Isle, N. J., 

 and owing to the favorable conditions afforded by the aquaria they 

 multiplied and became abundant During the past three seasons, 

 however, Dinophilus has not become abundant until late in the autumn 

 or in the early winter. The largest number of ova were gathered in 

 January and February, the number diminishing from that time, until 

 by May their nmnber was so small that it did not pay to collect them. 

 Diu-ing the past three years the animals have nearly all disappeared 

 by the middle of June. 



Fig. I. A and B, diagrams of ova with circumscribed loxodromic curves, 

 a-b, egg axis. Copied from Mead (1897). 



III. — Nomenclature. 



The nomenclature adopted in this paper is that modification of 

 Wilson's system (1892) used by Conklin (1897), with the further modi- 

 fication adopted by Child (1900) in prefixing coefficients to the macro- 

 meres, as well as to the micromeres. The macromeres are designated 

 by capitals, the micromeres by small letters. 



WTien the cleavage plane of two cells approximates the direction 

 of the loxodromic curve shown in text fig. I, A, it is dexiotropic ; when 

 it approximates the direction of that shown in text fig. I, B, it is 

 leiotropic. 



The number of the quartette is indicated by a coefficient. Thus la 

 is the member of the first quartette located in the A quadrant. The 



