BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [40] 



Pyrosoma is susj)ended by a thread in the mixture of alpohol and 

 hydrochloric acid in a cylindrical j ar, and, after a quarter of an hour, is 

 transferred to 60 per cent alcohol and gradually to that which is 

 stronger. G-ood preparations have been made by putting the colony 

 directly into 50 per cent alcohol. Care must be exercised to get rid of 

 the minute air bubbles which are apt to form on the surface of the col- 

 ony, though they usually disappear of themselves. 



The Salpidse include animals of very various consistency, from slimy 

 to cartilaginous. Certain species, furthermore, although they have con- 

 sistency when young, become soft in the adult stages and difficult to 

 preserve. Sometimes the Salpas when immersed in the fixing fluid 

 contract greatly, closing the orifices and dying in this condition. This 

 may be remedied by introducing a closed glass tube into one of the 

 openings, which, by allowing the entrance of theliquid, causes the animal 

 to resume its natural shape. 



The species with a hard body {Salpa hicaudata when solitary and 

 young 5 S. tilesi, both chain and solitary forms; /S. ^^o warm, both chain 

 and solitary forms), are immersed in a mixture of fresh water (100 

 c. c.) and concentrated acetic acid (10 c. c), where they remain for 

 fifteen minutes. Then they are washed in fresh water for ten minutes, 

 and then transferred gradually to alcohol, where it is necessary to float 

 the larger forms by means of pieces of cork attached to them with 

 threads so that the gelatinous sac shall not flatten down upon the 

 intestinal nucleus within. When treated in this manner, the animals 

 remain very transparent, crystals of marine salts forming in the tissues 

 much less than with the other liquids. 



The forms of medium consistency (young chains and solitary indi- 

 viduals of Salpa maxima and S. pinnata, young chains of S. bicaudata, 

 both the adult forms of S. fusiformis and S. democratica-mucronata) are 

 placed in the chrom-acetic mixture No. 1 for ten minutes and then put 

 directly into weak alcohol. 



The very soft forms (large chains of Salpa hicaudata and S. punctata, 

 both forms of S. maxima, 8. pinnata, and 8. virgola) are immersed in 

 the chrom-osmic mixture for from fifteen to sixty minutes, according to 

 their size. Then they are washed in fresh water and transferred to 

 weak alcohol. 



Very large specimens of Salpa maxima flatten out of their own 

 weight when put into weak alcohol. This may be obviated by blowing 

 a few bubbles of air into the cavity of the animal or by putting therein 

 a tube of thin glass closed at both ends to act as a float. The tube or 

 the bubbles of air should be removed before the animal is entirely 

 hardened. 



Professor Todaro, to preserve Salpas for histological purposes, 

 immerses them at first in Kleinenberg's solution, and after an hour 

 transfers them to alcohol. When ]3reserved in this manner, however, 

 all but the hard species lose their form entirely. 



