THE DEVELOPMENT OF OPHIOTHBIX FRAGILIS. 



583 



vacuoles and thus show obvious signs of degeneration. 

 When matters have reached this point the animal may bo 

 said to be in the first stage of metamorphosis. The changes 



Text-fig. 3. 



I)ia2[ram showing relations of organs in a full-grown larva of 

 Ophioilirix fragilis. ad. Adoral ciliated band. a.l. Antero- 

 lateral arms. int. Intestine, l.a.c. Left anterior cmloni. l.iiy. 

 Left liydrocojle. L.r.c. Left posterior coelom. m.p. Madreporic 

 pore. P.D. Postero-dorsal arm. r.L. Postero-lateral arms. P.O. 

 Post -oral arm. r.a.c. llight anterior coelom. r.hy. Kiglit lijdro- 

 orele. R.r.c. Right posterior coelom. ST. Stomach. stom. 

 Stomodajal portion of the oesophagus. 



Text-fig. 4. 



Diagram showing the changes which supervene during the first period 

 oi" metamorphosis. Lettering as iu preceding diagram; in addition: 

 l'.p'.c'. Ventral horn of tlie left posterior coelom. l".1'".c". Dorsal 

 horn of the left posterior coelom. 



which initiate metamorphosis are easily understood if the 

 two following text-figures be compared with one another. 

 Text-figure 3 shows the arrangement of organs in a larva 



