The accompanying figures are drawn from nature by the aid of the camera lucida and represent the relative sizes and shapes of like parts of several sponges. The statosphere is magnified about 35 times, the spicules of the skeleton, marked a, 150 times, all other figures 225 times. 1. Carterius tenosperma - Section of statosphere. (In the other genera these are without tendrils.) b, dermal or flesh spicule : d, birotulate spicule of outer coat of the statosphere. 2. Parmula Batesii - o, skeleton spicule : d, pannuliform spicule of statosphere. 3. Spongilla montana - a, skeleton spicule. 4. Meyenia fluviatilis - a, skel. spicule; d, birotulate star. spic. and disk of rotule. 5. Tubella Pennsylvanica - a, skel. spic.: d, inequibirotulate spic. of statosphere and disk. 6. Meyenia Leidii - a, skel. spic.; d, birotulate Stat. spic. and disk. 7. Uruguaya cora iioides - a, skel. spic 8. Spongilla lacustroides - b, dermal spic.; c. stat. spic. 9. Spongilla fragilis, var. minuta c, stat. spic. 10. Spongilla fragilis, var. calumeti - c, stat. spic. 11. Meyenia crateri-forma - d. birot. stat. spic. 12. Meyenia Everetti - d, birot. stat. spic. 13. Heteromeyenia argyrosperma - e, long, f, short, birot. stat. spic. 14. Heteromeyenia Kyderi - e, long; f, short; birot. stat. spicsion of the heavier silicious particles; whilst in clear lakes and rapidly flowing streams they plant themselves boldly upon the upper surface of stones in the full sunlight.

A further hint as to the bodies of water which favor their growth may be found in the fact that three species, one of them the most peculiar of American forms, were found in a stream a child could step over; five were gathered at one time in the submerged cellar of a burnt mill; while the timber-work of the dams upon some of our largest rivers has furnished rich collections; so that there is scarcely a situation where water stands or runs, excepting; upon the muddy bottoms of shallow streams or mill-ponds, where sponges may not be hopefully sought for and frequently discovered.

The best season for collecting sponges varies with the different species, but may be generally stated to be from the last of July to the middle or latter part of November, when the spicules and statospheres are likely to be fully matured. They may be preserved in dilute alcohol or dried by a few days' exposure to the air; in which condition (as the personal "application" of the foregoing sermon) the writer would be very happy to receive specimens from all parts of this and other countries. If packed in light boxes, strong enough to prevent crushing, the postage by mail (4th class) will be but one cent per ounce, which the writer will gladly repay, with any other reasonable expenses. He will acknowledge their receipt, giving names of known species and full credit to the collectors of all that are novel or interesting. Every gathering should be marked with its habitat, the date of collection, and the name and address of the sender.

A principal motive for the preparation of this at the present time is found in the desirability of securing as full a representation as may be, of the American forms at least, in a monograph now in course of preparation: - but contributions will always be very acceptable. Address, Edward Potts, 228 S. Third St., Philadelphia, Pa.