ZOOLOGY AND BOTANY, MIOROSCOPY, ETC. 71 



The ovum is splierical and its contents fairly transparent; the 

 stages preceding division are typical ; cleavage is much as in Pomato- 

 ceros, and is described in detail. After the sixteen-cell-stage the 

 ectodermal cells are those which increase most rapidly. The gastrula 

 is formed by invagination, and the blastopore shortly afterwards 

 becomes partly closed, and forms a small orifice which is pushed 

 towards the oral side ; this excentric position is to be explained by 

 the closure of the cleft taking place from behind forwards. The 

 primitive mesoderm-cells begin to be differentiated immediately after 

 the invagination of the ectoderm, and the process is typical in 

 character. 



The formation of the larval organs from the germinal layers is 

 next described, and it is stated that at the end of the embryonic 

 period the cell-nuclei and the cell-boundaries are not always to be 

 detected ; in the protoplasm of the cells the distribution of the yolk- 

 granules and the consequent change in colour, as well as the appear- 

 ance of new pigment-granules are to be observed. The red colour 

 which was at first general is gradually concentrated around the 

 equatorial cells which carry the circlet of cilia. The large pigment- 

 granules of the eye are new formations which appear at the end of 

 the embryonic period. 



The mode by which the body acquired its form is next discussed. 

 Some attention is directed to the nervous system ; this, it may be 

 supposed, resembles that of the larva of Polygordius, but it was not 

 possible to observe any other than the circular nerves. Close behind 

 the post-jral circlet of cilia two ectodermal vesicles appear on the 

 third day after fertilization, and after all the typical organs of the 

 trochophore-larva have been already developed. They each arise 

 from an ectodermal cell which grows inwards, and becomes hollowed 

 out by a vacuole ; it was not possible to determine whether this 

 " vacuole " makes its way in from the exterior. Later on mesodermal 

 cells become connected with each cell ; these structures are regarded 

 by Dr. Hatschek as being auditory organs. 



The canal of the head-kidney is formed by a single mesodermal 

 cell, which at first elongates in a spindle-shaped fashion, and then 

 forms a short rounded filament ; a lumen later on becomes apparent, 

 and cilia are developed which work backwards ; the hinder end of 

 the kidney extends to the close neighbourhood of the anus ; the 

 author directs especial attention to the fact that, at first, the hinder 

 protoplasmic swelling of the longitudinal muscle has exactly the 

 same relations as the other terminal cells of the head-kidney. 



The paper concludes with some notes on an allied larva from 

 Faroe, which is especially remarkable for having persistent auditory 

 vesicles in the hinder part of the cephalic region ; they are placed at 

 the anterior end of the ventral medulla, and externally to the 

 oesophageal commissure. 



Lumbrici with bifid ends.* — Prof. F. Jeffrey Bell gives an account 

 and figure of a Lumhricus terrestris with a bifid hinder end, and states 



* Aun. aiul Mag. Nat. Hist., xvi. (1885) pp. i75-7. 



