134 Dr. 0. Zacharias on the Reproduction and 



stuck up on their heads, pushed on one side, and in general 

 their existence is so completely ignored that it is wonderful 

 how, under such circumstances, the young Rotifers manage 

 to get developed. But in spite of the observer's wonder this 

 takes place, according to the temperature of the water, in 

 from five to eight days after the separation of the ovum from 

 the ovarium. The actual birth I have never been able to 

 observe, and it is to me quite a mystery through what portal 

 the young animal quits the body-cavity of the mother. 



We have still to glance at the anterior portion of the body 

 of Rotifer, which bears the two carmine-red eye-spots, each 

 furnished with a crystalline body. When examined from the 

 dorsal surface this section shows, in the first place, the trian- 

 gular ganglion, placed immediately in front of the masti- 

 catory apparatus. In Philodina roseola the eye-spots are 

 situated immediately over this triangle (in the nape), and it 

 looks exactly as if the animal carried about with it upon its 

 back the drawing of a fox's head with the snout in front. 

 The resemblance is striking, and by no means depends upon 

 a subjective notion. In Rotifer the anterior angle of the 

 triangle emits two hardly visible branches towards the two 

 eye-spots. Besides these there seems to me to be a union of 

 the same angle with the retractile organ which exists at the 

 extreme anterior end of the body, and bears a circlet of short 

 cilia, together with two long tactile seta3. The so-called 

 cervical lobe (erroneously named " respiratory tube ") is also 

 united with the cerebral ganglion by a commissure. Here, 

 no doubt, we have to do with a sense-organ, as is proved by 

 the fact that the animal (before passing from the contracted to 

 the extended state) protrudes this lobe to feel about, and 

 quickly retracts it again if a Paramecium or a Daphnia comes 

 in contact with it in swimming by. At its superior extremity 

 the organ bears a tuft of tactile setse. In fig. 3 I give a 

 superficial and lateral view of the anterior extremity of the 

 body in Rotifer, from which the reader may easily understand 

 the conditions which occur. 



When the rotatory organ is retracted it appears in the dorsal 

 view in the form of two semicircular plates, of which the 

 middle part refracts the light less strongly than the margin, 

 which appears somewhat inflated. On each side there is in 

 anatomical connection with the posteriorly directed horn of 

 these plates, a lobiform mass of substance, as to the interpre- 

 tation of which I am not quite clear. When the rotatory 

 organ is protruded the two lobes in question move somewhat 

 further forward, so that they appear to be half taken into that 

 organ. Have we to do here with salivary glands (besides 



