94 MCMURRICH. [Vol. XI. 



These, and the cells intervening between them and the anterior 

 teloblastic cells, form the lateral ventral bands, which have ap- 

 proximated much more closely to each other than in earlier 

 stages. No transverse band, such as was found in Jacra, can 

 be made out in this stage (its absence in earlier stages has 

 already been noticed), unless a patch of cells {DO?) lying in 

 the middle line between the two cephalic lobes is its repre- 

 sentative. This is possible, though another possibility, that 

 this patch represents a rudimentary dorsal organ, should not 

 be lost sight of. In the embryo figured another patch of cells, 

 which stained quite deeply, was found in the median line im- 

 mediately in front of the teloblastic cells ; I cannot discover 

 any special significance for these cells, which are indistinguish- 

 able in later stages, and regard them simply as naupliar cells of 

 the midline joining the two lateral bands. 



In the stage represented in Fig. 38 the teloblastic rows have 

 increased considerably in length, the rows originating from the 

 eleven primary teloblasts being longer than any of the others, 

 which decrease in length the further they lie from the median 

 line {compare in this respect Jaera, Figs. 25 and 26). The 

 teloblast row no longer forms a semicircle as in the previous 

 stage, but is now straightened out, indeed, is slightly concave 

 anteriorly. It has at the same time extended backwards over 

 the region previously occupied by the mes-endoderm, which 

 layer is unrepresented in the drawing, and it may be noted, too, 

 that all the teloblastic rows are parallel to each other, and have an 

 antero-posterior direction. The more lateral ones have not in- 

 creased in length very much when compared with the previous 

 stage, but the more median ones have, and it would seem that 

 the straightening out of the teloblastic row was due to this. ex- 

 cessive growth of the more median rows, which are conse- 

 quently pushed backwards, the lateral teloblasts remaining 

 fixed or being pushed outwards only. This explanation of the 

 change of form of the teloblast row was suggested in the de- 

 scription of Jaera, but the evidence in its favor is much more 

 pronounced in the present species. Special attention may be 

 directed to the median teloblastic row, the cells of which are 

 markedly different from those of the other rows, and constitute, 



