PRESERVATION OF THE HYDROIDA. 147 



or scraped, where promising growth appears, and the gathering 

 dropped into the bottles, to be examined elsewhere and in a 

 more comfortable position. This is really an excellent method 

 of obtaining material. 



Dredging is not likely to be undertaken by the occasional 

 collector unless he is a very enthusiastic one, and if undertaken 

 the individual will probably be in no need of advice from me, as 

 he will know more or less about it. To the beginner I would 

 say, choose a dredge of moderate size and confine dredging 

 operations to moderate depths, i.e. up to ten fathoms. If any 

 fishing industry is carried on where the collector happens to be, 

 he may get ample employment from a bucket of trawl refuse 

 obtained from one of the boats ; even the rejectamenta of 

 lobster-pots is a good hunting-ground. On an open sandy coast, 

 after a gale or heavy sea, deep-water specimens may be obtained 

 in excellent condition if the jetsam left by a receding tide is 

 carefully looked over. They should be promptly placed in bottles 

 of sea-water, to recover and expand their tentacles, and this 

 process may be aided by vigorously aerating the water by means 

 of a syringe. 



Having collected the material, the less eventful work of pre- 

 paring it for the microscope follows as a matter of course, and 

 I believe I am doing beginners a service in urging upon them 

 the desirability of arranging for this to take place at the earliest 

 possible moment after collecting. Once the hydroids begin to 

 feel the effects of overcrowding and badly aerated water the 

 polyps withdraw into their calycles, and require a large expendi- 

 ture of time and patience to coax them to expand again. The 

 best results are undoubtedly got when the collector is in a 

 position to go straight from the shore to his microscope and deal 

 with the material collected. The polyps are then vigorous from 

 their normal environment, less intolerant of the narcotising 

 agent, and a considerable quantity of material can be dealt with 

 in a comparatively short time, as there is no tedious waiting 

 for the polyps to expand. My own method is to divide the 

 collection into two lots, separating the Gymnoblastea from the 

 Calyptoblastea, as the former can be best prepared by killing 

 without the intervention of a narcotic. The hydroids are placed 

 in watch-glasses (or better still small Petri dishes) with clean 

 fresh sea- water, and cleansed as far as can be without injuring 



