54 SPERMATOZOON. 



of the spermatozoa while the segments of the nucleus give rise 

 to the main part of the heads. 



In many instances interstitial cells which do not give rise to spermatozoa, 

 are intermingled with the spermospores. 



In a good many cases, as first pointed out by Bloomfield 1 , the whole of 

 each spermospore does not become converted into spei'inatozoa, but part, 

 either with or without a segment of the original nucleus, i-emains passive, 

 and carrying as it does the off-budded spermoblasts may be called the 

 ' sperm-blastophor.' This passive portion of protoplasm is not employed 

 in the regeneration of the speruioblast. This very singular phenomenon 

 has been observed in Elasmobranchii, the Frog, the Earthworm, Helix, etc. 2 , 

 and probably has a much wirier extension. In Elasmobranchii (Semper) 

 the passive portions of protoplasm are nucleated, and are placed on the 

 outer side of the columnar spermospores which line the testicular ampullse ; 

 they are not distinctly differentiated till the nuclei, segmented from the 

 nucleus of the primitive spermospore to form the heads of the spermatozoa, 

 have become fairly numerous. In the Frog the passive blastophor also 

 occurs as a nucleated mass of protoplasm on the outer side of the spermo- 

 spore. In the Earthworm the blastophor forms a central non-nucleated 

 portion of the spermospore ; and the whole periphery of each spermospore 

 becomes converted into spermoblasts. 



It has been already stated in the introduction that the male and 

 female generative products are homodynamous, but the consideration 

 of the development of the products in the two sexes shows that a 

 single spermatozoon is not equivalent to an ovum, but rather that the 

 whole of the spermatozoa derived from a spermospore are together 

 equivalent to one ovum. 



1 Quart. Journ. of Micro. Science, Vol. xx. 1880. 



2 Bloomfield, /or. cit., p. So states that he has observed this fact in Lumbricus, 

 Tuhif'er, Hirudo, Helix, Arion, Paliulina, Bana, Salamandra, and Mus. 



