Of the exact method used by the fish in binding the nest together we are indebted to Prof. Ryder. The male fish spins from a pore or pores a compound thread, using his body to insinuate himself through the interstices through which he carries the thread. The thread is spun fitfully, not continuously. He will go round and round the nest perhaps a dozen times, when he will rest awhile and begin anew. Its shape is somewhat conical before completion. The thread is wound round and round the nest in a horizontal direction, and when freshly spun is found to consist of six or eight very thin transparent fibres, which have alternated tapering ends where they are broken off. Very soon after the thread is spun, particles of dirt adhere to it, and render it difficult to interpret its character. The nest measures one-half of an inch in height, and three-eighths in diameter. The time occupied in collecting materials and constructing the nest is about four hours, and when all is ready the male starts out to seek a female, and, having found her, conducts her with many polite attentions to the prepared home. The eggs being deposited, the male establishes himself as a guardian of the precious treasures, not even suffering the female to approach it again. Every fish that comes near, no matter how large, is furiously assailed. He gives battle valiantly, striking at their eyes and seizing their fins in his mouth. His sharp dorsal and ventral spines are very effective weapons in his defence. Constant watchfulness upon the part of the male is needed, for, if he go away for only a few moments, the sticklebacks and other fish lurking in the vicinity rush in and devour the eggs in an instant. A whole month he is occupied in providing for the safety of his offspring. About the tenth day he employs himself in tearing down the nest and carrying the material to some little distance. The fry may now be observed in motion. And these the male continually nurses, suffering no encroachment, and if the young brood show a tendency to stray beyond bounds, they are driven back within their precincts, until they are strong enough to provide for their own living, when both old and young disappear together.