•460 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



evidence has been found that amitosis is a factor in the regeneration 

 of the tadpole's tail. 



Scales of Freshwater Fishes.* — Arthur T. Evans has made a 

 study of the minute structure of the scales of various types — Perca 

 Jiavescens, Stizostedion vitreum, Boleosoma niyrum, various CentrarchidaB, 

 and the pike. His general result is that the minute features of scales 

 are very distinctive. Many striking similarities are seen between the 

 members of the same family. In every case the scales of the more 

 primitive fish show characteristics of primitive scales, and the scales of 

 the more specialized fishes show characteristics of highly developed 

 scales. 



Structure of Phallostethidse.t— C. Tate Regan describes the struc- 

 ture of l»oth sexes of Neostethas lankesteri g. et sp. n. and N. hicornis sp. n.^ 

 minute fishes in the family Phallostethidai. He compares them with 

 PhaUostethus dimckeri which he previously described. Very remarkable 

 is the complex priapium of the males. It seems to be an entirely new 

 formation ; its appendages, bones, muscles and glands are not to be 

 homologized with any structures found in the female fish or in other 

 Cyprinodonts. This suggests that intermuscular connective tissue may 

 give rise to cartilaginous or bony elements whenever and wherever the 

 necessity may arise. The precise use of the priapium in the intercourse 

 of the sexes cannot be determined without a study of the actual 

 behaviour. Its extraordinary complexity finds a parallel in the 

 mixopterygia of Selachians. 



Sea-water as a Medium for Tissue Cultures. :|: — M. R. Lewis has 

 shown from the success of numerous cultures that the dilution of sea- 

 water affords a simple and exact way ])y means of which can be obtained 

 a medium which is not only isotonic with the plasma of any given 

 animal, but which also contains the necessary salts in the same propor- 

 tion as does the plasma of the animal. 



In 1878 Fredericq showed that the blood and htemolymph of marine 

 invertebrates is isotonic with the sea-water, and in 1908 Macallum 

 showed that the plasma of higher animals is not changed in composition 

 from the sea-water, but is simply more dilute. The solution Lewis used 

 was formed from 90 c.cm. of the dilution of sea-water (isotonic with the 

 plasma of the animal), 10 c.cm. of bouillon made from the muscle of 

 the animal in question, 0*02 grm. of NaHCOg to neutraUze the acid 

 formed by the culture, and 0*25 grm. of dextrose to supply the energy 

 for the growth of the tissue. The cultures must be aseptic, and should 

 be kept in a warm chamber at 30° C. when the tissue is from a warm- 

 blooded animal, and at the temperature normal to the animal when the 

 cultnres are from the tissue of a cold-blooded animal. 



* Trans. Amer. Micr. Soc, xxxiv. (1915) pp. 255-68 (3 figs, and 1 table), 

 t Proc. Zool. Soc. London, 1916, pp. 1-26(4 pis. and 15 figs). 

 I Anat. Eecord, x. (1916) pp. 287-99 (4 figs.). 



