1032 JOTTINGS FROM BIOLOGICAL LABORATORY, SYDNEY UNIVERSITY, 



9. On the Embryology of Vermilia ccespitosa and Ewpomatus 



elegans. 



In both species artificial impregnation is readily effected, and 

 development proceeds with perfect regularity for at least two days 

 in a glass vessel with an occasional change of water. After this 

 period, however, abnormalities become frequent, and soon all the 

 embryos become more or less deformed, until at the end of three 

 or four days they all die off. To make the conditions as nearly 

 as possible natural I reared the embryos in bottles, the mouths of 

 which were closed with a piece of muslin; these wei'e suspended 

 by means of cords from the piles of a jetty in Port Jackson, or 

 were attached to a buoy, the bottles being so placed as to be 

 always immersed, but not far from the surface. 



About half an hour after the contact of ova and spermatozoa 

 yelk-division commences. Segmentation in Vermilia is equal and 

 regular, as in Serpula and Pomatoceros. When four cells are 

 formed the fifth and sixth are formed by the division of two of 

 these, and the seventh and eighth are formed by division of the 

 fifth and sixth.* 



A central cavity soon forms itself in the morula, and at about 

 the eighteenth to the twentieth hour invagination begins. A 

 slight flattening appears on one side of the blastosphere, the side 

 which is destined to become the posterior end of the embryo ; a 

 little on one side of this flattening a pit is formed, which growing 

 inwards gives rise to the archenteron. The blastopore, at first 

 nearly terminal, becomes shifted to one side of the larva, that side 

 destined to become the ventral. At the same time it becomes 

 elongated and slit-like, the anterior end of the slit widening to form 



*In Psygmohranchus Salensky (Arch, de Biol. t. III. pp. 345-378) describes 

 the segmentation as unequal. 



