.372 



mella oblonga of Ehrenberg, found in this country. It is closely 

 allied to Bracbionus. 



Developmen 

 males lay bo 



fertilized, like the summer eggs of the Cladocera (Daphnia). The 

 Rotifers live in damp places in water and revive after being 

 nearly dried up for a long time. Dr. Salensky has been the first 

 to give a complete sketch of the life-history of a Rotifer, Brach- 



The eggs of Bracbionus are attached by a stalk to the hinder 

 part of the body of the female. The following remarks apply to 

 the female eggs, which are quite distinguishable from the mascu- 

 line ones. The eggs undergo total segmentation, and the outer 

 layer of cells resulting from subdivision form the blastoderm, 

 when the formation of the organs begins. The first occurrence is 

 an infolding of the blastoderm (ectoderm) forming the primitive 

 mouth, which remains permanently open, the mouth not opening 

 at the opposite end as in Sagitta', but the entire development of 

 the germ is as in Calyptrsea, as Salensky often compares the ear- 

 liest phases of development of the Rotifer with those of that raol- 

 lusk. The "trochal disk," or velum, as we may call the ciliated 



ing on each side of the primitive infolding. Behind the primitive 

 hole appears another swelling, which becomes the "foot" or tail. 



There is soon formed at the bottom of the primitive infolding a 

 new hole or infolding, which is the true mouth and pharynx, while 

 a swelling just behind the mouth becomes the under lip. 



Soon after, the two wings of the velum become well marked, and 

 their relation to the head is as constant as in Calyptrsea. The 

 Fio- isu foot becomes conical, larger, and the termination 



of the intestine and anal opening is formed at 



The internal organs are then elaborated : fi«t 

 the nervous system, consisting of but a 

 pair of ganglia arising from the outer germ-taj* 

 (ectoderm). Soon after the sensitive hairs arise 

 on the wings of the velum. 

 Brachionu* nearly Fig. 184 shows the advanced embryo, with the 

 ready to hatch. body divided into se g me nts, the pair of cihat ?~ 

 swings of the velum (v), and the long tail (<)• At this time 1 * 



