1908] Davis. Life-history of Dolichoglossus. 201 



rendered partially opaque by accumulation of sediment. While 

 no special observations were made on the nature of these mem- 

 branes, it was noticed that, just before hatching, the outer one 

 became less transparent and less resistant. The latter-condition 

 is correlated with the hatching process which has already been 

 described. 



The particular feature of the egg in this stage is its opacity. 

 Bateson's statement that the egg of D. kowalevskii is "very 

 opaque" is equally applicable to that of D. pusillus. The opacity 

 is due to the yolk granules which are uniformly scattered through- 

 out the cell. This distribution is so uniform that no difference 

 such as described for the ascidian egg by Conklin and by Castle 

 may be seen distinguishing one part of the cytoplasm from 

 another. 



Cleavage. Although I obtained many hundred eggs and 

 larvae, I only succeeded in one instance in finding the earliest 

 stages. One lot contained a few unsegmented eggs and several 

 in early cleavage (four, eight, sixteen cells). The material was 

 insufficient for a study of the cell lineage. 



First cleavage. Bateson '84 (p. 209) says of the early cleav- 

 age: "The first furrow is formed in a median plane, dividing 

 the ovum into two equal parts. It passes to a considerable depth. 

 With regard to subsequent segmentation I have no certain ob- 

 servations; for though some of the ova divided into four and 

 eight nearly equal parts, these were obtained by artificial fertil- 

 ization, and the process of division was afterwards continued in 

 an entirely abnormal manner as mentioned above. Judging, 

 however, from the characters of the blastosphere, and from the 

 fact that yolk granules are uniformly distributed through the 

 whole tissue, there can be little doubt that the segmentation is 

 regular and complete. ' ' 



I am able to verify the above observations in regard to the 

 first cleavage. (Fig. 3, pi. 5.) 



Second cleavage. (Fig. 4, pi. 5.) The second cleavage is also 

 equal, the blastomeres being arranged at first in perfect radial 

 symmetry. In most cases this symmetry seems to persist, but in 

 a few there is a slight irregularity. This irregularity was at first 

 attributed to displacement due to manipulation. While this may 



