356 PilOF, E. A. MINCHIN ON THE BRITISH [DeC. 13, 



confidence in the coriectness of the identification of a species, 

 statements as to its occurience and distribution are of no value 

 whatever. 



III. Methods and Material. 



The present investigation has been directed mainly towards 

 a thorough examination of the spiculation. For making prepa- 

 I'ations of calcareous spicules, the reagent used by me is Eau de 

 Javelle. The piece of sponge selected is first of all, in the case of 

 spirit-specimens, placed in water for a minute or tv/o, and then 

 put into a test-tube with a small quantity of Eau de Javelle, 

 barely more than enough to cover the bit of sponge. In a few 

 minutes the soft parts are dissolved, and with gentle shaking the 

 sponge disappears, being I'esolved into a cloud of spicules. No 

 heating is necessary, but the Eau de Javelle loses its powers aftei- 

 a few months, and should have been recently made up. The test- 

 tube is then filled up with distilled watei', shaken up well, and 

 put aside to stand undisturbed until the spicules have fallen to 

 the bottom, which they do in the course of a few hours. As much 

 as possible of the liquid is then decanted ofi", care being taken not 

 to disturb the spicules settled at the bottom, after which the test- 

 tube is again filled up with distilled water, shaken up, and left to 

 settle again. After a third washing with distilled watei- in this 

 way, the Eau de Javelle is sufiiciently removed, and the tube is 

 then filled up with strong alcohol (90 per cent.), in which spicules 

 settle much more cjuickly than in water*. After two washings 

 with alcohol, the spicules are ready to be mounted. This is done 

 simply by drawing them up with a pipette from the bottom of 

 the alcohol in the test-tube, placing them on a slide, and burning 

 off the alcohol, leaving the spicules dry on the slide. A drop of 

 Canada balsam is then put on them, and on that a cover-slip. 

 In this way very clean preparations of the spicules can be obtained. 

 It is advisable, however, not to defer the examination of them 

 too long, as even in Canada balsam they become corroded sooner 

 or later, and in some samples of the mounting medium the coi- 

 rosion proceeds rapidly. Hence attention should be paid to the 

 purity, that is to say the non-acidity, of the Canada balsam 

 employed. 



For drawing the spicules I have used in all cases a cameia 

 lucida with Zeiss's ocidar II. and objective D, giving a magnifica- 

 tion of 320 (reduced in the illustrations in this memoir to 300). 

 My method is first to draw the commoner forms of spicules seen, 

 and then to hunt carefully through the slide and draw every 

 spicule found difiering at ail markedly from those already drawn.. 

 The process is a tedious one, and it is too tiring to attemj^t the 

 examination of more than two specimens a day at the utmost. 

 But only in this way is it possible to frame an idea of the great 



* The process of washing the spicule can be greatly hastened bj' using a centri- 

 fugal machine, but as there is great danger of their then becoming caked through 

 interlocking of the spicule-raj-s, I have preferred the slower and surer method 

 described above. 



