Development o/Rotifer vulgaris. 135 



the above-mentioned stomachal glands) ? This I do not 

 know. 



I have still to say a few words about the muscular system 

 and the " pedal glands." As to the function of the latter we 

 have only recently ascertained anything. With Ehrenberg 

 these " clavate, turbid, elongated bodies " were problema- 

 tical organs. In interpreting them he hesitated between 

 muscles and sexual glands. We now know that they are the 

 seat of a secretory activity, and secrete a sticky product, 

 which serves to attach the animal to smooth surfaces. As 

 regards the muscles, I shall content myself with stating that 

 the masticatory apparatus and contractile vesicle possess 

 special muscles, while elsewhere longitudinal and transverse 

 muscles are present. The latter were regarded by Ehrenberg 

 as blood-vessels. In Rotifer we observe in the region of the 

 head a complex ramification of muscular fibres, which cannot 

 be specially traced. There is no circulatory apparatus for the 

 blood in any Rotifer. The blood occupies the body-cavity 

 quite freely, and its movement is maintained by the contrac- 

 tions of the body. True blood-cells cannot be recognized ; 

 but at all times fine fusiform and rounded elements are sus- 

 pended in the body-fluid, which very probably functionally 

 represent blood-cells. 



IV. The Embryonic Development of Rotifer vulgaris. 



When we have a great number of specimens of Rotifer at 

 command, we always find one or more of them in which the 

 constriction of the ovum from the ovary may be traced. There 

 is first produced a small swelling on the latter. On close 

 observation this proves to be densely packed with vitelline 

 granules, so that the gradually increasing raised portion stands 

 out clearly by its darker and granulated appearance against 

 the ovary, which remains clear. It now appears as if all the 

 vitelline formative material collected together at a single point 

 of the ovary. Something of the same kind must also have 

 been recognized by previous observers in other species of 

 Rotatoria. Thus Leydig describes the ovary of Notommata 

 centrum, and says : — " Only one half of it has vitelline 

 granules, among which again numerous darker spots of accu- 

 mulation are to be recognized." Upon the horseshoe-shaped 

 ovaiy of Pterodina patina the same author also remarks as 

 follows : — " In one limb we distinguish the germinal vesicles 

 with their germ-spots and the finely granular vitelline mass 

 between them ; the other limb displays scarcely anything but 

 vitelline substance, the molecules of which are here larger." 

 Similar observations were also made by Prof. Leydig upon 



