entoderm has apparently begun to thicken. 



The stage following this is usually as represented in 

 Fig. 9. Here we see a large circular mouth. The eight an- 

 gles of the peristome are produced into eight tentacles nearly 

 of a size and still very small. The stem has begun to length- 

 en and to show its characteristic" structure. Larvae at this 

 stage, are normally quite firmly attached to some foreign body, 

 but retain their swimming pavers some time longer. ^%en re- 

 moved from its seat, such a larva will sv/im about as before, 

 only more slowly, rotating on its long axis, with its stem end 

 forv/ard. An interesting exception to this mle was found in 

 a larva Fig. R, that while still actively swimming with stem 

 undeveloped, had four of its tentacles of about the same size 

 as in Fig. 9, while tlie four tentacles that alternate with 

 these were twice as long. This arrangement of the tenta- 

 cles reminds one of Aurelia, where four tentacle ^ first appear 

 and these are followed by four others alternating with them. 



Fig. 30 is from an obliquely longitudinal section of a 

 larva in the same stage as Fig. 9. This section cuts the lar- 

 va in an adradial plane, that is, in a plane that bisects the 

 angle between two tentacles, the eight tentacles being, four 

 perradial and four interradial. Fig. 31 is another section 

 I of the same series. It cuts the larva tangential ly and sho'vs 



