300 E. A. MINCHIN. 
Fic. 8.—Spicule complete. The founder apparently wandering off, the 
thickener at the proximal extremity. 
Figs. 9—18.—Development of the large curved monaxons of L. 
complicata, as seen in surface views of the wall of the sponge. 
Tic. 9.—Lance-head between the two nuclei of the formative cells, the 
separation between which is as yet scarcely indicated. 
Fie. 10.—Lance-head with the two formative cells at each extremity. 
Fic. 11.—Similar stage, the lance-head much thicker; the shaft of the 
spicule growing rapidly in length. 
Fig. 12.—Later stage; the thickener commencing to leave the completed 
lance-head. 
Fig. 18.—The lance-head abandoned; the activity of the thickener shown 
by a distinct rim (7.) on the shaft. 
Fie. 14.—Similar stage; the rim (7.) formed by the thickener very distinct. 
The founder in its progress has encountered a ray of a triradiate system (r.¢.s.), 
producing a distinct kink in the spicule (4.). 
Fic. 15.—Similar stage. 
Fig. 16.—Similar stage in the variety of the large monaxons which is with- 
out a lance-head. 
Fies. 17, 18.—Spicules nearly fully formed, showing the two formative 
cells close together at the proximal extremity of the spicule. 
Figs. 19—29.—Development of the triradiates and quadriradiates 
of L. complicata as seen in surface views. The nuclei seen at a 
higher focus in the preparation are coloured more deeply than those 
seen at a lower focus. | 
Fras. 19, 20.—Two sextetts in which the first trace of spicule-formation is 
seen in the form of irregular granules. In one instance the granules are in a 
distinct vacuole. 
Fie. 21.—Sextett containing three small pieces of calcareous matter, one 
larger than the others, and evidently taking shape as the unpaired ray. 
Fig. 22.—Septett containing a large and distinct unpaired ray and traces 
of one of the lateral rays and of the gastral ray. 
Fic. 23.—Sextett with small triradiate, lying in a clear. space limited by a 
distinct sheath. 
Fie. 24.—Small quadriradiate with six basal formative cells and gastral 
actinoblast with two nuclei. : 
Fies. 25, 26.—Small quadriradiates with still a single nucleus in the 
gastral actinoblast. 
Fie. 27.—Small triradiate with six formative cells. 
