1888.] MICROSCOPICAL JOURNAL. 45 



of natural selection favors those growing on the lower side of their bases of 

 support, which protect them from the intrusion of the heavier particles. 



For that reason perpendicular and water-logged or floating timbers, sub- 

 merged stumps of trees, and branches drooping into the water from trees or 

 bushes along the banks, are favorite locations. They do not disdain more 

 temporary support, such as weeds and water grasses. I have received from 

 a friend, specimens growing upon water plants that wild ducks had torn from 

 the bottom, and that were found floating upon the surface of Lake Michigan. 

 Through the clear water of our northern lakes, we may often see them lying 

 in slender lines upon the leaves of submerged weeds, or in beautiful cushion- 

 like masses upon the stones or gravel. 



In my explorations I have had much satisfaction in the use of a long pole, 

 to which was attached a small net, with one part of its edge shaped into a 

 scraper, like a garden hoe. This enabled me to examine the surface of tim- 

 bers at a depth of eight or ten feet and to tear oft' and bring up sponges from 

 that depth ; beyond which all is to me an ' aqua incognita.' Biologists 

 labor at some disadvantage in studying the fauna of our fresh water, as com- 

 pared with the facilities oftered them in collecting ocean subjects. The nets 

 and dredges of many exploring expeditions have, at least, begun to acquaint 

 us with the inhabitants of the 'deep sea;' but who knows anything about 

 the fauna or the flora of our deep fresh-water lakes, or even of our larger 

 streams? The largest specimens of this group ever reported were dredged 

 from the bottom of Lake Baikal in Central Asia (^Lubomirskia) . I know^ 

 of no similar attempts to collect them elsewhere. It is to be hoped that 

 means may be found ere long to make such explorations, which must result 

 in an increase of knowledge in many lines. Meantime no opportunity oftered 

 by the accidental or designed drainage of artificial reservoirs should be 

 neglected. I have spent hours of great pleasure and profit while groping 

 around the distributing reservoirs upon Fairmount Hill, Philadelphia, at 

 times when the water was drawn oft' for cleaning or repairs. 



One further point as to methods of collecting and I shall finish this section 

 of my subject. Unless our sponges are large, it is difficult to detach them 

 without mutilation from the rough .surfaces of stones. It is therefore prefer- 

 able to gather, when possible, those growing upon wood, which may be 

 sci-aped or chipped without injury to them. It is essential to secure the very 

 lowest portions, as it is there the gemmules often abide. 



The proper season for collecting fresh-water sponges, in w%Tters of the 

 temperate zone, depends upon the purpose of the collector. If it is his de- 

 sire to gather cabinet specimens merely, for the identification of old or the 

 determination of novel species, it is hardly worth while to begin before July. 

 As with the flowering of plants, the maturity of different species of sponges 

 is attained at various dates, between mid-summer and late in November. 

 The essential point is, that the gemmules and their armature shall be fully 

 perfected ; and when that condition is attained in any specimen, thei-e is no 

 reason for further delay. 



I would, however, recommend to intending students a far higher object 

 for their ambition ; — that is, the study of the physiology and life history of 

 sponges as members of a sub-kingdom whose position has been greatly 

 questioned and whose character, derivation and subsequent evolution are very 

 important and- perplexing topics. I would have such workers search for 

 and examine them at all seasons of the year (even in mid-winter, when I 

 have never failed in suitable situations to find some in a growing condition) , 

 keeping memoranda as to each species separately ; noting the date of their 

 germination or earliest appearance, the locality, elevation, temperature ; 

 rapidity of growth at different seasons ; time and manner of formation of 



