544 CRESSWELL SHEARER. 



products are brought together, and material can be easily 

 obtained of any stage. The trocliophores can be readily 

 reared to the adult worm in small jars of sea-water to which 

 sufficient food is added from time to time, in the form of 

 cultures of the common Diatom Nitzschia closteriuui. 

 On this they rapidly grow, and soon attach themselves to 

 the sides of the culture jars and form their tubes. 



The minuteness of the egg is a serious disadvantage, how- 

 ever, in following the changes that lead up to the establish- 

 ment of the trochophore. The fully formed larva barely 

 measures 65^ in diameter, and the pre-trochophoral stages 

 are very small, and the cells of the blastulas and gastrula3 are 

 unusually minute. In following the origin and growth of 

 the head-kidneys one is forced to depend almost wholly on 

 sectious, and sectioning larva? of this size is a tedious 

 proceeding. 



In the Serpulid Poinatoceros I soon found a more 

 suitable object in which to trace the development of the 

 head-kidneys. The egg is larger and more deeply pigmented. 

 In the arms of the '"' cross-cells " this pigment quickly 

 becomes segregated on development, where it affords a ready 

 means of orientation. For these reasons I early abandoned 

 the study of Eupomatus for that of Pomatoceros, on 

 which I hope shortly to complete my "Studies on the 

 Development of Larval Nephridia,'^ by publishing a 

 full account of the origin and growth of these organs in 

 this animal. 



The pi'esent notes dealing with Eupomatus, although 

 incomplete, I have thought worthy of publication, as they 

 deal with the formation of the trochophore and the appear- 

 ance of the coelomesoblast. They derive some importance 

 from the fact that on this Annelid, Hatschek (17) conducted 

 his classical investigations on the development of the meso- 

 blast bauds — investigations which have played so prominent 

 a part in all our speculations concerning the mesoderm. Any 

 revision, therefore, of the subject on the same material as 

 that studied by him is not without interest. 



