ON THE EMBRYOLOGY OF THE ECTOPROCTA. 15 



PLATE I. 



rig. 1. Median longitudinal section of a young embryo. 

 Fig. 2. Median longitudinal section of an older embryo. 



PLATE II. 



Fig. 3. Median longitudinal section of an embryo almost ready to 

 be hatched. 



Fig. 4. Transverse section of an embryo of the age of (ig. 3 (more 

 highly magnified), passing through the region of the brain and pyriform 



. The manuscript of the above paper was received by Prof, de Lacaze-Dutbiers in 

 the beginning of August, 1887. Since that time I have had an opportunity of 

 becoming acquainted ■with two memoirs by Dr Ostroumoff on the Polyzoa of the 

 Gulf of Sebastopol. I regret that it was not possible for me, during the correction 

 of my proofs, to take into consideration the results arrived at by this observer. 



