EXPLANATION OF PLATE. 



Figure I. A group of zooids from a colony of Ectinascidia turbinata (XI). 

 Figures 2 & 3. Pseudoceros found on E. turbinata, freshly removed (X 5). 

 Figure 4. The same individual as that shown in figures 2 and 3, five hours 

 after removal from its host (X 5). 



Figures 5 & 6. The same individual, two days after I'emoval from its host; 



Fig. 6 is a ventral view (X 5). 

 Figure 7. Pseudoceros found inside the tunic of a dead Ascidia atra (X 2). 



The figures are by Miss H. E. Fernald. 



