468 Mr. H. J. Carter on the 



portion is spiniferous in the spined and smooth in the smooth 

 anchoring- spicules. 



Fig. 3. Spiniferous anchoring-spicule of Meyerina claviformis, Gray, 

 showing form of head or free end : a, position of the cross ; b, un- 

 dulating line. 



The only difference between this and the spiniferous anchoring- 

 spicule of Labaria consists in the prominence and number of the 

 undulations of the line on the head, too slight for specific 

 distinction, although showing still more strongly that these un- 

 dulations are prolonged into spines in Euplectella. Figs. 1-3 

 are all on the scale of l-24th to l-1800th of an inch. 



Fig. 4. Spiniferous anchoring-spicule of Euplectella aspergillum, showing 

 form of head or free end, where the spines or arms are Literal 

 and much recurved : a, undulating line ; b, end of central canal 

 terminating in a lash of branches ; c, position of the cross on 

 central canal. 



Fig. 5. The same, in which there are eight spines or arms uniformly 

 arranged round the head, and based respectively upon the pro- 

 jections of a, the undulating line ; b, position of the cross on 

 the central canal. 



Figs. 4 and 5 we on the scale of l-12th to l-1800th of an 

 inch. 



Fig. 6. Spiniferous anchoring-spicule of Holtenia Carpenteri, showing 

 form of head or free end : a, position of the cross on the central 

 canal. Here there is no undulating line, on account of the 

 thinness of the head. Scale l-24th to l-1800th of an inch. 



Fig. 7. Portion of the shaft of a spiniferous anchoring-spicule of Holtenia 

 Carpenteri, showing the distant but still spiral arrangement of 

 the spines : a, proximal end ; b, spines ; cc c, spines, made a 

 little lighter to represent their being on the opposite side of the 

 shaft. 



Fig. 8. Portion of the shaft of a spiniferous anchoring-spicule of Meyerina 

 claviformis, showing a more crowded, but still spiral, arrange- 

 ment of the spines : a, proximal end ; b, spines ; cc c, spines on 

 the opposite side of the shaft. 



Fig. 9. . Portion of the shaft of a spiniferous anchoring-spicule of Hyalo- 

 nema Sieboldii, Gray, showing a still more crowded condition of 

 the spines, which are here grouped into lines arranged round the 

 shaft more or less in a continuous spire ; also that they are sup- 

 ported on bracket-like projections of the shaft: a, proximal 

 end ; b, spines ; ccc c, spines on the opposite side of the shaft ; 

 d, groups in continuous spiral ; e, minute tubercles or aborted 

 spines ; f, spines broken off. 



N.B. The specimen of Hyalonema from which this drawing 

 was made was dredged up on board H.M.S. ' Porcupine ' in the 

 Atlantic Ocean, somewhere off the coasts of Great Britain and 

 Ireland. The body is just 1^ inch long, and the thickness of 

 the spicule of course very small compared with that of an adult 

 form, which, if relatively magnified, would exceed the whole 

 width of the plate. Moreover the portion selected for mounting 

 and drawing was taken out of the body and not from the stem, 

 where the spines soon get rubbed off, although they may be 

 afterwards frequently found lying on the shaft, as at /. The 

 minute tubercles e, often accompanying the groups of spines, 

 are the remains of such as never went beyond this stage of 

 development, as the whole group of spines and tubercles com- 

 mences in this way in the upper part of the anchoring-spicule 



