JENNINGS: DEVELOPMENT OF ASPLANGHNA HERRICKIL 117 



EXPLANATION OF PLATES. 



All the figures represent preparations of the eggs of Asplanchna Herrickii de 

 Guerne, except Figure 29, Plate 4, which represents the egg of Asplanchna prio- 

 donta Gosse. All were drawn, with the aid of the Abbe camera lucida, to a mag- 

 nification of 525 diameters. 



The four blastomeres of the four-cell stage are distinguished by different colors, 

 and the same color is retained througliout for all the cells (constituting a " quad- 

 rant ") derived from each of the four blastomeres thus distinguished. The quad- 

 rant A is blue ; B, orange ; C, yellow ; and D, red. 



The prominent granulations in the ventral portion of quadrant Z) are figured; 

 but all other granulations are omitted, except in the case of Figure 7, wliere the 

 general granulation is also represented, though somewhat diagrammatically. 



For an explanation of the system of nomenclature used in lettering the cells see 

 page 16. In some cases for want of room the letters have been omitted, the expo- 

 nents only being expressed. In such cases the color indicates to which quadrant 

 the cell belongs. 



In all the figures where it is possible, the animal pole of the egg is above, the 

 ventral pole below. In views of the dorsal or ventral poles of the egg, the anterior 

 end is above. Unless otherwise stated, figures represent surface views of more or 

 less transparent eggs; these are shaded, whereas sections — optical or actual — are 

 not shaded. 



ABBREVIATIONS. 



hl'po. Blastopore. d. pol. Polar cell. pol. anm. Animal pole. 



