SPERMATOZOA OF SUANCHA AND STCON. 301 



size between the individuals of this erupt cloud and his " minute wandering 

 cells " in the substance of: the sponge-wall. He concluded that these 

 remarkable little cells, sometimes spherical but more often elongated, arise 

 by the repeated division of "clear amosbocytes." His observation also was 

 on Gruancha {Claihrina) coriacea. (Note A, infra, p. 315.) 



Ever since 1887 it has been an unsolved puzzle to me why excretory 

 granules should be localised about the afferent pores, through which the 

 whole supply comes on which the sponge's life is based. Minchin points out 

 tills difficulty (1897, p. 527) as applying to the pore-cells, though not to 

 the oscular porocytes and apical-ray cells. But through the afferent pores, 

 besides oxygen and food, must enter what is (on ordinary assumptions) 

 equally important for the survival of the species, namely spermatozoa. 

 I suggest that the odoriferous nature of the excretion of the porocytes 

 attracts the spermatozoa of the species which fall on the surface of the 

 sponge, so that they make their way to the pores themselves and enter 

 through their lumen into the flagellate cavity, and that this is the advantage 

 of the extraordinary position of these excretory cells. It will be remembered 

 that similar cells are also aggregated at the other opening into the flagellate 

 cavity, on what I called in Ascaltis cerebrum (1891, p. 3) "the granular 

 lip" and Minchin (1897, p. 495) " the oscular rim." (Note B, infra, p. 316.) 

 The employment of an excretion to serve a useful purpose gives explanation 

 of the origin of many new organs throughout the animal kingdom, and I have 

 elsewhere (1892 h and d) suggested that the skeleton of the horny sponges 

 has its origin in the same granules of these excretory cells*. The utilisation 

 of the odoriferous properties of an excretion, both to repel and to attract, are 

 well known in higher animals. 



In regard to the fainter smell of the Calcaronea, it will be remembered that 

 in this group, even in Leucosolenia, " the pylocyte is annular and generally 

 lies at the bottom of a funnel-shaped depression or afferent canal " (1898 c, 

 p. 73). Minchin (1908, p. 323) declined to see any difference in shape 

 between the pylocytes of Leucosolenia and Clathrina, though his drawings 

 illustrate it admirably ; but he confirmed the funnel-shaped depression in the 

 former. This, and the commonly rougher surface of Leucosolenia, suggest 

 the possibility that Calcaronea have free-swimming spermatozoa, and Calcinea 

 have amoebuloid spermatozoa, and that the pylocytes which lead from the 

 funnels of Leucosolenia or the deep afferent canals of Sycon and Leucandra 

 are not noticeably granuliferous, because the spermatozoa of these genera 

 remain swimming and do not creep. If this be true, it is only advantageous 

 for the spermatozoa of Calcaronea to be attracted by the granules of the 



* Cotte (1903, p. 562) opposes this view very strongly, maintaining that spongin is a 

 molecule of high energy. But whatever energy can be proved to have gone into the spongin 

 molecule is in a completely unavailable form, for there are few more stable substances 

 known. 



LINK. JOUHN. — ZOOLOGT, VOL. XXXIV. 1'.". 



