428 



SCIENCE 



[N. S. Vol. XXIX. No. 741 



anal was a functional gut in the adult of certain 

 Devonian sharks. In these forms { Cladoselachids ) 

 the anal fin was paired, its elements converging 

 at the base of the tail, where the cloaca was 

 accordingly located. The sub-caudal position of 

 the cloaca is, moreover, indicated by the position 

 of the kidneys. These are now known, both by 

 macroscopic and histological characters in these 

 fossils to have continued behind the ventral fins 

 and converged near the tail. 



The Cause of Pulsation in Soyphomedu^ce : Alfeed 



GoLDSBOBOUGH Matee, Carnegie Institution of 



Washington. 



In the case of Cassiopea xamachana the sodium 

 chloride of the sea water is a powerful stimulant 

 to the nervous system, but its tendency in this 

 ■direction is exactly ofi'set and coxmteracted by the 

 inhibiting influences of the magnesium, calcium 

 and potassium. Thus the sea water as a whole is 

 a balanced fluid, and neither stimulates nor in- 

 hibits the pulsation of the medusa. 



The stimulus which causes pulsation is due to 

 a slight but constantly maintained excess of 

 sodium chloride over and above its concentration 

 in the sea water. This excess of sodium chloride 

 is engendered in the distal endodermal cells of 

 the marginal sense-organs, which constantly give 

 rise to sodium oxalate. This oxalate precipitates 

 the calcium chloride and sulphate which enter the 

 sense-club from the surrounding sea water, and 

 forms the calcic oxalate crystals of the sense-club, 

 thus setting free sodium chloride and sulphate, 

 which act as powerful nervous stimulants to 

 which the nervous elements respond periodically. 



The stimulus-producing pulsation is thus wholly 

 internal, not due to external agencies. It has been 

 commonly supposed that the crystalline concre- 

 tions in the sense-clubs of scyphomedusae were 

 calcium carbonate, but I find upon chemical an- 

 alysis that they are oxalates. 

 The Sense of Hearing in the Dogfish: G. H. 



Paeker, Harvard University. 



If the side of a large wooden aquarium in which 

 a dogfish (Mustelus oanis) is swimming quietly 

 is struck a vigorous blow, the dogfish will react 

 by a quivering motion, especially of the posterior 

 edges of the pectoral fins. By the use of a heavy 

 pendulum the momentum with which a given blow 

 was struck could be determined. The momentum 

 of the minimum blow to which normal fishes 

 reacted was arbitrarily called unity. After the 

 eighth nerves were cut a blow with a momentum 

 three or four times that just mentioned was 

 needed to produce a reaction. This response was 



believed to be due to the mechanical stimulation 

 of the skin. After the skin of a normal fish had 

 been rendered insensitive by cutting the fifth, 

 seventh and lateral line nerves, and by coeaining 

 the pectoral regions, a step not taken in pre- 

 vious experiments, the fish was found to be as 

 sensitive to sounds as a normal fish is. This sen- 

 sitiveness entirely disappeared when in addition 

 to the operations already carried out on the fish, 

 the eighth nerves were cut. Sounds affect both 

 the skin and the ears of the dogfish and the latter 

 organs are the more sensitive of the two. 



Regulation in the Morpho genetic Activity of the 



Oviduct of the Een: Ratmond Peael, Maine 



Agricultural Experiment Station. 



This paper gives an account of a case in which 

 a gradual change in the shape of eggs successively 

 laid by the same bird occurred. This change in 

 the shape of the eggs is (1) referable to a change 

 in the activity of the oviduct, (2) definitely pro- 

 gressive and (3) regulatory in character, since 

 it proceeds from the abnormal to the normal. 

 The first egg laid by a particular Barred Plymouth 

 Rock pullet (No. 183) was strikingly abnormal in 

 shape (long and narrow). Every egg laid by this 

 bird was saved and measured. As eggs were suc- 

 cessively laid there was a gradual change in shape 

 from the abnormal condition found in the first 

 eggs to a substantially normal condition. 



The change in the shape of the eggs was found 

 to follow a logarithmic curve, of the type seen in 

 growth curves. 



The Nature of the Stimulus which Causes a Shell 

 to 6e Formed on a Bird's Egg : Raymond Peabl 

 and Frank M. Sdeface, Maine Agricultural 

 Experiment Station. 



This investigation was undertaken to determine 

 precisely what is the nature of the stimulus which 

 excites the reflex activity of the shell-secreting 

 glands of the oviduct in birds. These possibilities 

 were to be considered: 



1. That the stimulus is mechanical, and arises 

 from the presence of a soft body (the egg) within 

 the " uterus " or " shell gland." 



2. That the stimulus is chemical in nature. 



3. That the activity of the shell-secreting appa- 

 ratus is controlled directly by the functioning of 

 other parts of the reproductive system. 



If shell formation is caused from the mechanical 

 stimulation of the " shell gland " by the egg it 

 would be expected that any foreign body intro- 

 duced into that portion of the oviduct would have 

 a shell formed around it. It was found to be 

 impossible to introduce a foreign body of any size 



