SEXUVL ORGANS AND THEIR PRODUCTS IN PHORONIS. 



151 



a small, spherical and compact-looking nucleus (fig. 6, f). In an early 

 stage of the spermatogenesis we see that nucleus greatly condensed and 

 transformed into a slender elongate shape, curved after the manner of 

 the letter C (fig. 6, g). The bent nucleus is then seen to grow somewhat 

 in thickness and greatly in length (h and i), eventually to stretch out as 

 the head of the filiform spermatozoa (J), of which the tail is about twice 

 as long as the head. 



