Introduction to Animal Morphology. 83 



minute anal opening" described by Corda, Leydtgy and 

 Hancock. A second race of buds may form on the 

 growing bud before its detachment : indeed, as many 

 as five such progenies have been found united. This 

 process is frequent in summer. 



Sexual reproduction is commonest in autumn, but 

 is not confined to any season. The spermigenous 

 organs form near the base of the tentacles (Fig. 10, sp.) 

 At one spot, the interstitial ectodermal cells enlarge, 

 and become polyhedral, and with them are found 

 amoeboid cells. The neighbouring neuro-muscular 

 cells thin out, and form a coating over this now conical 

 or wart-like growth. The nuclei in the altered cells 

 disappear, and their contents become granular and 

 confluent. Then from the amoeboid cells, oval re- 

 fracting spermatozoa (Fig. II, B) form, and become 

 flagellate, and escape into the surrounding water 

 through an apical opening in the papilla. 



The ova also develop in the interstitial tissue, near the 

 proximal or aboral end (Fig. 10, 0). There, in one or two 

 separate projections of the ectoderm, cells increase, and free 

 nuclei appear in the surrounding intercellular protoplasm. 

 In each projection, one central, amoeboid, vacuolated cell con- 

 taining granules and vitellin particles increases in size, and a 

 nucleus or germinal vesicle appears within it, around a 

 germinal spot (Fig. 11, C). Green pigment grains, and 

 sharply-contoured, round masses (pseudo-cells), like the yelk 

 granules of a spongilla-egg, develop within this cell. After these 

 form, the germinal vesicle becomes indistinct. They are fer- 

 tilized in situ, the head of the spermatozoon touching the outer 

 wall of the egg ; whereupon the yelk segments, each part 

 exhibiting amoeboid motions, and the egg becomes a morula, 

 whose inner cells are polygonal and the outer cylindrical. 

 The outer surface of the egg is at first smooth, then becomes 

 rough with irregular projections, and dark. The cylinder cells 



G 2 



