Mabch 27, 1914] 



SCIENCE 



473 



firmly fastened to some solid, the long leg riseg up 

 45 to 90 degrees from the sole and bears on its 

 outside a spiral ridge of six or more turns, while 

 its mouth is completed by a reflexed lip. Three 

 factors enter into the making of this case: the co- 

 ordinated contractions of the body; the behavior 

 of the cilia; a special secretion. The first factor 

 determines the form of the case, which is then a 

 permanent record of the secretory ' ' instincts ' ' of 

 the animal. The animal first assumes the shape 

 of the future foot of the case and secretes this 

 about itself. Then by a special set of contrac- 

 tions of the anterior part it forms a mould upon 

 which the spiral tube is made, turn by turn, with 

 the measured elongation of the rest of the body. 

 Finally, by an entirely unexpected change in form 

 of the mould the Up of the mouth is added. The 

 only part of the animal in contact with the case 

 is the point of permanent attachment to the bot- 

 tom of the case, elsewhere the secretion is laid 

 down as a hardening mass separated from the 

 body by the length of the cilia. As the secreting 

 progresses from the foot up the cilia pass through 

 successive states, at first rigid and quiet, then 

 specially active in limiting the inner face of the 

 case wall. 



In the posterior end is a special organ, some 10 

 by 20 microns in diameter, associated with the 

 myonemes. 



In response to contact with solids of some kinds 

 the posterior en-d puts out an adhesive secretion 

 that, apparently mechanically, influences other 

 Folliculiixas, so that from the free-swimming state 

 they commonly settle down in colonies, each with 

 its separate case, but all fast to a common pellicle 

 spread over the solid object or even over the sur- 

 face film of quiet water. 



The case is secreted when the specialized frontal 

 field and lobes are not yet present. 



The Beactions to Light and Darkness of the Me- 



lanopliores of Frog Tadpoles: Davenport 



Hooker. 



The tadpoles of Bana pipiens were used as sub- 

 jects for investigation and some seventy-five series 

 of experiments were performed. Each series ex- 

 tended over a number of days and each tadpole 

 was subjected to a variety of conditions. The 

 light used in the experiments was either direct 

 sunlight or the light of a 75-candle-power Wels- 

 baoh mantle. To obtain total darkness, the tad- 

 poles were placed in blackened light-tight boxes 

 or in an unilluminated dark room. 



The following results were obtained: 



1. The melanophores in the subepidermal layer 

 of connective tissue of tadpoles respond to light 

 and darkness in the opposite manner from those 

 in the corium of adult frogs, with which they are 

 identical. The former expand in response to light 

 and contract in response to dark. 



2. The epidermal melanophores do not respond. 



3. The color of the background has no effect on 

 the nature of the response in tadpoles. 



4. The transition from the larval to the adult 

 type of response takes place after metamorphosis. 



5. Continued exposure to darkness produces a 

 secondary reaction of expansion of the melano- 

 phores in the tadpole. This follows the primary 

 reaction of contraction by an average of six hours. 



6. To again obtain contraction of such expanded 

 melanophores, the tadpole must be exposed to light. 

 The Movements of the Dog-fish as Determined by 



Olfactory Stimulation: G. H. Parker. 



A normal dog-fish, when confined in a large 

 pool, swims more or less continuously back and 

 forth, turning at the ends of its course. When ex- 

 cited by food, it courses over the bottom of the 

 pool, turning now to the right, now to the left. 

 This form of locomotion does not occur when the 

 nostrils are occluded with cotton. Hence the food 

 excitation is an olfactory response (Sheldon). 

 When excited by food, a normal fish turns about 

 as often to the left as to the right and generally 

 exhibits a course like a figure eight. When only 

 the left nostril is occluded, the fish turns predom- 

 inately to the right; when the right nostril is 

 plugged, predominately to the left. In each case 

 the predominating turns may be as many as 90 

 per cent, of the total turns. These observations 

 lead to the conclusion that, in seeking food, the 

 dog-fish commonly turns toward the more vigor- 

 ously stimulated nasal organ. 

 The Oxygen Utilisation of Fishes: G. G. Scott. 

 Internal Pressure in Spo7iges: G. H. Parker. 



The internal pressure under which the current 

 of water flows through a sponge was measured 

 hydrostatically and found to vary in eight species 

 of marine sponges from one to four millimeters of 

 water. In Spinosella sororia an average finger 

 discharges under a pressure of about three milli- 

 meters of water 78 liters of water a day. A col- 

 ony of twenty such fingers would discharge about 

 1,575 liters a day, or over 415 gallons. Sponges 

 move large volumes of water at very low pressure. 

 A Study of the So-called Life Cycle in Oxytricha 



fallax and Pleurotricha lanceolata: George A. 



Bait SELL. 



