28 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



past the sides of the body from above, certain thickeuings of the epiblast or 

 skiu layer will be noticed. These thickenings are surmounted by trans- 

 parent cells which project freely for a little distance from the general 

 level of the surface. The cells to the number of ten or twelve are some- 

 what separated from each other, and have blunt truncated tips which 

 are not surmounted with sensory hairs or filaments. As compared with 

 the similar structures in the young cod, which have sensory hairs sur- 

 mounting them, they differ in having the i^eculiar, somewhat separated 

 truncated transparent cells clothing their surface externally, while in 

 the former nothing is seen from above but a smooth rounded elevation. 



Spinning habits and structure of the male. — The male binds the nest 

 together by means of a compound thread which he spins from a pore or 

 pores behind the vent, while he uses his bobbin-shaped body to insin- 

 uate himself through the interstices through which he carries his thread 

 with wliich he binds a few stalks of Anacharis or other water- weeds 

 together, bringing in his mouth every now and then a contribution of 

 some sort in the shape of a bit of a dead plant or other object, which he 

 binds into the little cratUe iu which the young are to be hatched. The 

 thread is spun fitfully, not continuously. He will go round and round 

 the nest for iDcrhaps a dozen times, when he will rest awhile and begin 

 again, or turn suddenly round and force his snout into its top with a 

 vigorous, plunging motion as if to get it into the proper shape. Its 

 shape is somewhat conical before completion, an oi^ening remaining at 

 the top through which it is suj^posed he introduces the eggs. The thread 

 is wound round and round the nest in a horizontal direction in the case 

 we are describing, and if this thread is placed under the microscope 

 when freshly spun, it is found to be composed of ver.y thin transparent 

 fibers to the number of six or eight ; where they are broken off they 

 have attenuated tapering ends as though the material of which they 

 were made had been exhausted when the spinning ceased. Very soon 

 after the thread is spun jjarticles of dirt adhere to it and render it diifi- 

 cult to interpret its character. I have seen the thread being drawn out 

 from the abdomen repeatedly, but not from the vent ; it appeared to me 

 more probable that it came from the openings of a special spinniijg 

 gland. Its glass-like transparency shows that it is not made uj) of in- 

 gested food, the particles which would exhibit themselves were that the 

 case. The nest measures half an inch in height and three-eighths in 

 diameter. 



Upon opening the male I find a large vesicle filled with a clear secre- 

 tion which coagulates into threads upon contact with water. This vesicle 

 appears to open directly in front of the vent, separately from the latter. 

 It measures one-fifth inch in length and an eighth iu diameter. As soon 

 as it is ruptured it loses its transparency, and whatever secretion escapes 

 becomes whitish after being in contact with water for a short time. 

 This has the same tough, elastic qualities as when spun by the animal 

 itself, and is also composed of numerous fibers, as when a portion is taken 



