Figure 43. Later stages of development of medusa Pelagia 

 noot-iluca (by Krohn) . 



a — anterior; b— -posterior end of the body; 

 stomach. 



The development of worms54 Krohn described in many 

 separate reports. In 1851 he wrote an article on the 



54 . Of the types of worms known in the mid- nineteenth 



century, many were distinguished later on in independent 

 groups of forms, including phoronids and chaetognaths , 

 and are so listed. 



571 



