E. MAESHALLI. — KEPKODUCTIVE ELEMENTS. 179 



IttproducilcG Eleiiieals. 



All tliat we know about the ova and spermatozoa of the 

 Hexactiuellida is the little that was reported by F. E. Schijlze 

 ('80, '87) from E. aspergillum. As his remarks in this connec- 

 tion are brief, I ma}- here quote them in full : 



' In the connective substance, finally, occur the genital 

 products, the sperm masses and ova, in more or less abundance, 

 and usually in the same individual. The sperm masses, both 

 in young and mature stages, are exactly like those of other 

 siliceous Sponges, such as Renicm. In their immature form the 

 ova are indistinguishable from connective-tissue cells. They sub- 

 sequently increase in size and develop refracting yolk granules, 

 and exhibit a very characteristic aspect owing to the enlarge- 

 ment of the nucleus. It is remarkable that in the adult (0.3 mm. 

 in diameter), irregularly roundish ova of E. aspergillum, along 

 with which ripe sperm masses also occurred, the nucleus was 

 situated not in the ovum itself, but lay free in a superficial 

 depression into which it had been squeezed. This expulsion of 

 the nucleus was probably the result of the drastic preservative 

 treatment. 



' It is curious that I have never been able to discover any 

 distinct segmentation stages. It would not, howevei', be justi- 

 fiable to jump to the conclusion that the ova leave the body of 

 the Sponge as such, and undergo subsequent development out- 

 side the mother organism.' (F. E, Sch., '87, p. 24). 



The numerous sperm-balls, and also ova of different sizes 

 (up to 300//. in dia. and 'filled with round yolk-granules'), 

 were found both in the inner and in the outer trabecular frame- 



