Helminth Fauna of the Dry Tortugas. 175 



by the head and neck, which are so small as to be easily overlooked by the 

 collector. In its expanded condition this peculiar organ is a disk with 

 fimbriated edges. Each of the primary divisions has a tendency to divide, 

 some of them nearly to the base. The diameter of the central, undivided 

 part is 4 mm. The radiating divisions and the undivided central portion 

 are all profusely frilled and folded. The minute scolex is often lost in 

 detaching the worm from the mucous membrane of its host. 



16. Scolex polymorphus Rudolphi. 



Report U. S. F. C, 1886, pp. 3, 4, plate \i, figs. 8, 9. Proc. U. S. Nat Mus., 

 vol. xix, pp. 789-792, plate i, figs. 4-15. Bull. U. S. F. C, 1899, pp. 270- 

 284, and 413, etc., noted under 28 hosts. Bull. Bureau of Fisheries, vol. 

 xxiv, p. 332, etc., noted under 34 hosts. 



The literature of this title is very extensive. Without doubt it has 

 been used as a specific name to designate the larvae of a great variety of 

 cestodes belonging to many different genera. It is a convenient term, how- 

 ever, and in my papers is to be understood to refer to small larval cestodes 

 found free in the alimentary canal and bile-duct of many fishes. 



Since these forms are evidently possessed of great powers or resist- 

 ance to the digestive juices of fish in general, they doubtless often pass a 

 longer or shorter time of sojourn in each of many hosts, related to each other 

 as eater and eaten. Ultimately they attain the adult state in some selachian. 



These larvae were not found in many of the Tortugas fishes which were 

 examined in the season of 1906, nor were they at all abundant in those 

 situations in which they were found. 



Following is a list of the finds of this larva: 



July 7. A few small larvae were found in the intestine of a grouper 

 (Epinephelus striatus). The bothria were without costae, and there was 

 no red pigment in the neck. 



July 10. Several larvae were observed in washings from the alimentary 

 tract of a frigate mackerel (Au.vis thazard}. These were small, active, 

 with no red pigment, but with a distinct costa on each bothrium. 



July ii. Several small larvee were seen in washings from the alimentary 

 canal of a black grouper (Mycteroperca bonaci}. 



July 5 and 9. A few were found on the first date and several on the 

 second in the gray snapper (Lutianus griscus). They were small, active, 

 with prominent and distinct anterior sucker, and simple bothria. The water 

 vascular system was distinct, especially at the posterior end. 



July 6. A few were found in the yellow-tail (Ocyurus chrysurus}. 

 These were small, with the rudiments of a costa on each bothrium, and two 

 small red pigment spots in the neck. They were very active. 



