STUDIES ON THE TREMATODES OF WOODS HOLE. III. THE LIFE CYCLE OF MONORCHEIDES CUMINGIAE (MARTIN) WITH SPECIAL REFERENCE TO ITS EFFECT ON THE INVERTEBRATE HOST

¹ From DePauw University and the Marine Biological Laboratory, Woods Hole, Mass.

1. The life cycle of Monorcheides cumingiae (Martin) involves the development of sporocysts, cercariae, and metacercariae in the marine bivalve, Cumingia tellinoides, and the development of the adult, under experimental conditions, in the flounder and eel.

2. Another clam, Tellina tenera, can serve as an alternative second intermediate host and on one occasion was found to act in the capacity of a first intermediate host.

3. Attempts at hatching the eggs of this trematode failed. Therefore it seems probable that the eggs must be eaten by the clam before further development will take place.

4. In spite of the extremely heavy infections, the clams survived for several weeks with no more food than would be obtained from the daily changes of sea water.

5. A free-swimming period is apparently necessary before the cercariae will encyst. This is an advantage to the parasite in increasing its range.

6. The cercariae encyst in large numbers in the siphons, particularly the incurrent, and foot. Metacercariae are found in smaller numbers in the gills, mantle, and, very rarely, in the visceral region.

7. There is a marked change in the staining reaction of the nuclei of recently encysted and older metacercariae. When both receive the same treatment, the nuclei of the young metacercariae take up little or no Delafield's hematoxylin while the nuclei of the older metacercariae are heavily stained.

8. Although the metacercariae seem to induce the surrounding clam tissues, particularly in the foot, to increase the deposition of a darkly staining material, this substance does not inhibit super infection.