1908] Davis. Life-history of Dolichoglossus. 205 



longer be seen from the surface but sections show that it does not 

 completely close until about six hours later. 



Larva within the egg-capsule. The larval period may be said 

 to begin with the closure of the blastopore and elongatiorLof the 

 body. This elongation is at right angles to the plane of the ciliary 

 band. I was, unfortunately, not able to determine the relation 

 of the axis of the embryo to the first cleavage plane. 



The most important changes that take place are: growth in 

 length, enlargement of the ciliary band, appearance of the pos- 

 terior collar groove and later of the anterior groove ; and devel- 

 opment of the anterior, or apical cilia. (Figs. 13, 14, pi. 6.) 

 As these changes are fully described by Bateson '84 and are so 

 closely repeated in the present species I need not here discuss 

 them. 



Period II. 



The larva remains through this period, in external appear- 

 ance, just as when leaving the egg, except perhaps for a slight 

 elongation of the body. (Fig. 15, pi. 6.) The significance of 

 this quiescent stage has already been discussed in another con- 

 nection. 



Period III. 



Like period I, this period is marked by many changes : further 

 elongation of body, both of proboscis and body proper; appear- 

 ance of gill openings; disappearance of apical cilia, and, later, 

 reduction of the ciliary band ; increase in diameter and width of 

 collar. (Fig. 16, pi. 6.) I have nothing to add to Bateson 's 

 (pp. 211-213) full description of the external appearance of the 

 stages of this period. My own observations, except for slight 

 details, agree with his. 



Internal Features. Period I. 



Blastula. The first internal change to be noticed is in the 

 latter part of this period. The cells forming that portion of the 

 blastosphere which is to be invaginated (endodermal portion) 

 are somewhat irregular, having rounded ends projecting un- 

 evenly into the blastocoele. (Fig. 18, pi. 7.) They are relatively 

 narrower than the cells of the opposite portion of the blastosphere 



