BULLETIN OF THE UNITED STATES FISH COMMISSION. 247 



wood, Introd., 11,511, I find, makes a similar observation in regard to 

 the larva? of the gnat or mosquito famJly. He says: "The head is dis- 

 tinct, rounded, and furnished with two inarticnlated antennte, and sev- 

 eral ciliated appendages, which serve them for obtaining nourishment 

 from their food." 



The fixed Tunicates are probably as dependent upon the microscopic 

 life swimming about them in the water as the Lamellibranchs. The 

 Barnacles in like manner, immovably fixed during their adult existence, 

 kick their minute food into their mouths with their filiform legs, as 

 remarked by Huxley. In Pedicellina aniencana, abundant in Saint 

 Jerome's Creek, I have observed that there are rows of vibratory cilia 

 continuous with those of the tentacles around the edge of the lopho- 

 phore, which appear to lie in grooves, which blend on either side of the 

 excentrically placed mouth. In this manner the microscopic food of 

 this curious bryozoan is conveyed in ciliated grooves to the mouth 

 from all points of the oral disk. With these we may close our survey 

 of the modes in which the i)rotozoan grade of life is ai)propriated 

 the smaller Arthropods, Pteropods, Polyzoa, Annelids, and Tunicates, 

 but we must remember that upon these again the larger loims 

 subsist, which are either food for each other or for man. As we 

 pass in succession the larger forms, we may note the Lamellibran- 

 chiates, with this garniture of vibratory cilia covering the gills and 

 palps, and which carry the particles of food and sediment suspended 

 in the water used in respiration to the mouth to be swallowed. The 

 Clupeoids and Cetiorhinus with their branchical sieves are particularly 

 noteworthy for the perfection of the apparatus of prehension, but we 

 must not forget that the gill-rakers of all fishes, whenever developed to 

 any extent, probably subserve a similar function. Lastly, the right- 

 whales, with their closely ranged plates of baleen suspended from the 

 upper jaws, forming in reality a huge strainer or filter for the large 

 volumes of sea-water which pass through the mouth, and from which 

 the food of these marine giants is so simply obtained, will enable us in 

 a measure to comprehend the importance of the minute life of the world, 

 and its indirect but important economical relation to man. . 



THE FOOD OF THE YOUNG SHAD. 



The periods of yeUc-ahsorption. 



In a previous paper by the writer on the retardation of the develoji- 

 ment of the shad, it was stated that the yelk-sack disappeared on the 

 fourth to the fifth day after the young fish had left the egg. Although 

 this statement is in a broad sense true, I find upon more accurate in- 

 vestigation that there is a small amount of yelk retained in the yelk-sack 

 for a much longer time. It appears in fact that there are really two 

 periods of absorption of the yelk which may be very sharply distinguished 

 from each other. The first extends from the time of hatching to the end 



