132 REPORTS OF INVKSTIGATIONS AND PROJECTS. 



egg. The latter may be due to the formation of some substance with high 

 osmotic pressure which absorbs sea-water and pushes the membrane outward. 

 Attempts to determine the osmotic pressure of this hypothetical substance 

 with hypertonic sea-water failed because the membrane was very freely 

 permeable to the salts of sea-water. The formation of the membrane appears 

 to be secretory in nature. 



It was found that double membranes could be formed by treating sperm- 

 fertilized eggs with CHClg-saturated sea-water. This took place at the two- 

 cell stage also and less distinctly as far as the early blastula. Attempts to 

 produce double membranes in other ways failed. 



Owing to the scarcity of sea-urchins about Tortugas this year, a further 

 study could not be made. Most of the above work on eggs was made possible 

 by two cruises of the PhysaUa to the Marquesas Keys, the experiments being 

 performed on board. 



Since this report was written, a paper by R. Lillie (Biol. Bull., vol. 17, page 188, 

 1909) has appeared in which the same view is supported, namely, that an increase in 

 permeability of the plasma membrane is the essential condition for the initiation of 

 development in an egg. 



The Trematodes and Cestodes of Tortugas, by H. S. Pratt, of Haverford 



College. 



During the month I spent at the Marine Biological Laboratory of the Car- 

 negie Institution of Washington at Tortugas, I collected material for the 

 morphological study of the trematodes and cestodes of the region. To 

 obtain the former teleostean fishes and loggerhead turtles were collected, 

 while the cestodes were found in selachian fishes. 74 teleosts belonging to 20 

 species were investigated and about 30 species of trematodes obtained from 

 them, while 5 species of trematodes were obtained from 2 loggerhead turtles ; 

 7 selachians, of which 5 were sharks and 2 were rays, were investigated and 

 about 10 species of cestodes and i of trematodes obtained. 



The trematodes in the loggerhead turtles were found in the stomach, 

 duodenum, small intestine (not including the duodenum), and rectum. Three 

 species were obtained from the stomach, one of which belongs to the genus 

 Plesiorchorus and is closely allied to P. cymbiformis, which occurs in the 

 same turtles in the Mediterranean. Two other species, closely allied to 

 Cyuiatocarpus iindiilatus and Rhytidodes gclatinosus of the Mediterranean 

 turtle, were also found. One of these, the Cyniatocarpus, was represented 

 by many hundreds of individuals in the duodenum of each of the turtles 

 examined, although C. undulatus is rather an unusual form in the Mediter- 

 ranean turtle, having been found by Looss in only 2 out of 14 turtles exam- 

 ined by him. The anatomy of these chelonian trematodes and their relation 

 to those occurring in other parts of the world will be the subject of a paper 

 which will be published in the near future. 



Of the large number of 30 species of trematodes found in the teleostean 

 fishes examined, about 60 per cent occurred in the intestine of their hosts, 

 about 8 per cent in the stomach, 12 per cent in the pyloric appendages, 8 per 

 cent in the duodenum, and 12 per cent in the rectum. These worms were 

 found in most cases in small numbers in their hosts, sometimes but i or 2, 

 rarely more than a dozen individuals of a species occurring in a single host. 

 In the few cases in which the individuals of a species were numerous in a 

 single host, the pyloric appendages were usually the seat of the infection. 



