SPERM 89 



mitochondrial material. They also stain with methylene blue, not a 

 mitochondrial stain. Rothschild (1952) thinks that the middle piece 

 probably contains enzyme complexes, such as the cytochrome system 

 and that this is suggested by the presence in it of mitochondria-like 

 structures. The middle piece of Arbacia can be isolated by a special 

 technique involving the removal of heads and tails (Di Stefano and 

 Mazia, 1952) ; these authors think that the middle pieces are the center 

 of ribonucleic acid activity. A preliminary paper on the isolated 

 middle pieces has been published recently by Nefr(i953). Popa (1927) 

 also isolated certain components of the sperm by destroying others. 



The tail of the Arbacia spermatozoon consists of about ten separate 

 fibrils of uniform thickness, each fibril having a diameter of about 

 50 mix (0.05 [i.), as shown in electron microscope pictures (E. B. Harvey 

 and Anderson, 1943). Electron microscope pictures of sperm of other 

 animals show that the fibrillar structure is characteristic of sperm tails, 

 e.g., the squid (Schmitt, Hall, and Jakus, 1943) and the bull (Baylor, 

 Nalbandov, and Clark, 1943). Many years ago, separate fibrils were 

 observed (and figured) in the tails of many different kinds of 

 sperm, of birds, insects, fish, amphibia, and reptiles, by Ballowitz 

 (1888, 1890) in teased material, with an ordinary light microscope. In 

 the chaffinch, he found 7-1 1 fibrils, somewhat as are found in Arbacia. 



The structure and reaction to stains of the sperm of Arbacia punctulata 

 have been especially studied by Popa (1927). He was particularly 

 interested in the distribution of fats, which he found present in the 

 head, middle piece, and tail. The peculiar forms of the spermatozoa 

 which he observed with different stains can be duplicated by treatment 

 of living sperm with distilled water, drying, etc. (E. B. H.). In distilled 

 water, the heads swell to double their volume (E. B. Harvey and An- 

 derson, 1943). 



Figures of the spermatozoon of Arbacia lixula given by Pictet (1891) 

 and by Retzius (1910) show it to be similar to that of ^, punctulata. 

 The acrosome or perferatorium and the two spherical bodies in the 

 middle piece are figured by Retzius on his Plate XV, no. 2. The 

 measurements of A. lixula sperm given by Field (1895) are similar 

 to those of ^. punctulata. 



Recent photographs of sperm of other species are those of Vasseur 

 (1947) of Echinocardium cor datum ; of Tyler (1949 c) of Lytechinus pictus 

 taken with the electron microscope; of Rothschild (1951a) of Echinus 

 esculentus ; of J. C. Dan (1952) of two Japanese species (also Dan, 1954, 

 Biol. Bull. 107 : 335-349 and AfzeHus, 1954, Zeit. f. Zellforsch. 42 : 

 134-148). 



