CHAPTER 12 



Sperm 



a. Morphology 



The spermatozoon of Arbacia punctulata consists of a pointed conical 

 head, a middle piece the shape of a flattened cyhnder and a long thin 

 tail (Fig. ii). Measurements of the living sperm are (approximately): 



HEAD MIDDLE PIECE TAIL 



Since the volume of the egg is 212,000 [jl^, the sperm is only about 

 I /30,000th the volume of the egg. Using another egg and other data, 

 Needham (1931, Chem. Emb. p. 1251) arrived at the same figure. 



The spermatozoon of Echinus esculentus, roughly the same shape, has 

 been studied by Rothschild. He has calculated from photomicro- 

 graphs that the volume of the whole sperm is about 18 y.^, of the head 

 and middle piece about 10 [x^ and of the middle piece not more than 

 5 jjL^; he found difficulties in measuring the radius of the sperm tail, 

 but says it lies between 0.3 and o.i [jl (Rothschild, 1950b, d; 1951a; 

 1952). According to Pictet (1891) the diameter of the tail of all sea 

 urchins is about 0.2 [i. It has been found, in general, that the species 

 of sea urchin which have large eggs also have large sperm (E. B. Har- 

 vey, 1942). The egg of Echinus esculentus has a diameter of 180 [jl and that 

 of Arbacia punctulata 74 |j., so that one would expect the spermatozoon 

 of Echinus to be larger. 



The conical head of the spermatozoon of Arbacia punctulata appears 

 to be a mass of chromatin, staining black with Heidenhain's haem- 

 atoxylin, without any special structure. The tip, the acrosome or per- 

 feratorium, however, stains with methyl green and Janus green, mito- 

 chondrial stains, and with methylene blue. Popa (1927, p. 251) says 



