MATERIALS FOR A MONOGRAPH OF THE ASCONS. 573 



for some valuable suggestions to my friend Mr. H. A. Miers, 

 Fellow of Magdalen College and Professor of Mineralogy in 

 the University of Oxford. Professor Miers pointed out to me 

 that there were two possibilities as regards the early develop- 

 ment of the spicules ; either tiiat the rays when first secreted 

 are of a non-crystalline nature, and become crystalline as the 

 result of contact and fusion ; or that the rays are crystalline 

 from the first. In the latter case there would be two further 

 alternatives to be considered, namely, that the rays might be 

 at first three separate crystals independently orientated, or 

 that the rays, even when distinct from each other, might 

 possess a molecular structure similarly orientated throughout 

 the whole system. 



Since these possibilities can be tested without difficulty by 

 examining very young spicules between the nicols of a polar- 

 ising microscope, I have searched through my preparations for 

 the early stages of the development of the spicules. The pre- 

 parations which are figured in this paper, being mounted in 

 glycerine, and now for the most part more than two years old, 

 are so much corroded by the glycerine that the youngest stages 

 are almost all dissolved entirelv : but I have found a number of 

 young spicules in preparations mounted in Canada balsam, 

 which are scarcely or not at all corroded. Besides three 

 minute spicules in preparations of the adult coriacea, I have 

 examined an embryo of contorta, two embryos of cere- 

 brum, one of falcata, and one of reticulum. Of these 

 only the embryos of cerebrum showed slight traces of cor- 

 rosion ; in the other embryos the spicules did not seem in the 

 least damaged, though the preparations are eighteen months 

 old. Slight corrosion, it may be pointed out, would not affect 

 the crystallographic results, so long as the spicule be not com- 

 pletely dissolved; but in the case of the embryos of cere- 

 brum it affects the question of the separation of the rays. 

 Since the parts last deposited seem to be the first to be cor- 

 roded, it is possible that in ray preparations of cerebrum 

 spicule rays which appear distinct had really become united 

 a,nd then separated again by corrosion. If so, my results with 



