SMALLWOOD. — POLTCERELLA ZOOBOTRYON. 611 



quently rests on its back. The foot may be fully expanded or much 

 contracted. When the animal was placed in a weak solution of 

 methylene-blue in sea-water, the cup-like folds on the rhinophores 

 appeared as swellings, and after a few hours the lateral papillae and 

 rhinophores were sloughed off. 



" The eggs are laid in a cylindrical mass of jelly. The number varies 

 from one hundred to three hundred in each mass. Each animal lays 

 several egg-masses. 



"The animals are very hardy, living in confinement for over six 

 weeks." 



11. The Systems of Organs. 



The several systems of internal organs of Polycerella zoobotryon are 

 so compactly grouped that it makes their interpretation difficult. The 

 thin integument is rendered quite firm by the presence of numerous 

 rod-shaped spicules. Between the integument and the various inter- 

 nal organs there is what remains unoccupied of the secondary body 

 cavity, or coelom. In gross dissection one can recognize the anterior 

 portion of the digestive system, consisting of the short buccal region, 

 the dorsal suctorial bulb, and the ventral odontophore. The esophagus 

 is distinguished with difficulty from the several reproductive ducts. 

 The nerve collar of ganglia is so minute as to be made out only with 

 fairly high powers of the dissecting microscope. Immediately posterior 

 to the above organs lies the two-parted visceral mass, nearly concealed 

 on the dorsal side of the liver and kidney chamber. The remaining 

 portion of the secondary coelom is filled by the oval posterior visceral 

 mass, which is composed of the liver and the hermaphroditic glands, 

 bearing on their dorsal surface the stomach-intestine, kidney, and 

 heart. The exact relationships of these several organs can be made 

 out only by the aid of stained sections. Whole animals were fixed in 

 either Hermann's fluid, Mliller's fluid, or a picro-acetic mixture, the 

 first two giving the best results. After remaining in Hermann's fluid 

 for ten days, admirable adequately stained sections were secured, 

 which have enabled me to make out some of the more perplexing con- 

 ditions of the minute anatomy. Several specimens left in Hermann's 

 fluid for three weeks were useless because they had become so brittle. 

 Sections were made in the three principal planes of the body ; these, 

 together with dissections of several of the organs, have furnished the 

 material for this study. 



The observations on the living animal and the collection of the 

 material were made in January, 1909, at the Bermuda Biological Sta- 

 tion. I desire to express to the Director, Professor E. L. Mark, and to 



