310 SUMMARY OF CURRENT RESEARCHES RELATING TO 



to evaporate from tbeso slowly, as, if hurried over a lamp, each spicule 

 is often margined with minute globules that it is impossible afterwards 

 to remove. However, when the slide is apparently quite dry, it may be 

 6afely exposed a moment to the heat to make sure of it, and then covered 

 with balsam and glass as usual. 



The author adds : — " The investigator has now before him all the 

 elements necessary for solving his specific problem, according to the 

 formulae which follow : — The normal sponge, the dermal film, the trans- 

 parent gemmule, and a display of the detached spicules. Neither would 

 alone answer, but the series will settle all points, excepting in the case 

 of the genus Carterius. When this is suspected, the gemmules should 

 first bo examined dry ; and, in preparations for mounting, great care 

 should be taken to avoid the destruction of the tendrils (cirri), by the 

 prolonged use of strong acids. Expert microscopists will improve their 

 gemmule mounts by dividing some of them with a thin knife, endea- 

 vouring to make the section through the foraminal aperture ; this, in the 

 case of species having long birotulates, such as Myenia crater iformis, is 

 of the utmost importance. 



" ' Seniors ' in microscopy will please pardon the minutiae of the pro- 

 cesses just given, as they were necessary to make them available for the 

 freshmen. All are reminded that the above directions as to collection 

 and examination refer to mature sponges only. It is seldom safe, or 

 even possible, to name one in which no gemmules can be found. If a 

 course of study is undertaken, involving the histology and physiology 

 of fresh-water sponges, many peculiarities will of course be observed 

 that have not been alluded to here. One of them concerns the develop- 

 ment of the spicules, and, if not understood, will pretty certainly mislead 

 the beginner into the supposition that he is examining a novel species. 

 Both the skeleton and the dermal spicules of young sponges are fre- 

 quently marked with bulbous enlargements at the middle, and often 

 half-way between the middle and each end of the spicule. These seem 

 to indicate an immature condition, as they disappear when the spicules 

 are fully formed." 



Potato Cultivations.* — Dr. J. Eisenberg, instead of using solid 

 pieces of potato, employs a mash. The potatoes are first well cooked by 

 steaming, and then pounded in a mortar. The mashed potato is then 

 pressed down into small glass pans about 5 cm. in diameter. The pans 

 are provided with a lid in which there is a groove, so that the cover may 

 fit accurately. The pans are then sterilized for three successive days, 

 for half an hour a day, in a steam sterilizer. "When required for use, the 

 cover is lifted up and the surface inoculated. To make the pan air- 

 tight, it is only necessary to turn it down on the cover, and run some 

 melted paraffin round the angle between the lid and the pan. If there 

 should be any condensation water on the lid this can be got rid of by 

 passing the pan through the flame of a Bunser's burner two or three 

 times. 



Sterilization of Potato, Apples, and Water for cultivation pur- 

 poses.t — Dr. H. Plaut first sterilizes three or four test-tubes (3 cm. broad 

 and 20 cm. long) which have been plugged with cotton wool in the 

 usual way. Potatoes are then peeled with a clean knife, while apples 



* Centralbl. f. Bakteriol. u. Parasitenk., iii. (1S88) pp. 216-7 (1 fig.), 

 t Ibid., pp. 100-1, 126-8 (1 fig.). 



