Maech 3, 1S99.] 



SCIENCE. 



315 



ferred from the life habits of a form •which 

 encysts during periods of drought. For 

 the ability to undergo suspended anima- 

 tion necessitates such specialization that 

 it is improbable that evolution operated 

 through such an encj'sting foi-m (which is 

 absolutely helpless and inactive until it is 

 set free into the water), in bringing about 

 a vertebrate which breathed air the year 

 around. 



Reference was also made to the breeding 

 habits o{ Polypterus, and an accessory copula- 

 tory organ in the male — a modified anal fin 

 — was described. The breeding season fol- 

 lows the inundation of the Nile. 



The general collections, some of which 

 were exhibited, brought back by the Senfi" 

 zoological expedition, are intended for 

 general distribution to qualified investiga- 

 tors, who can work up the material within 

 a reasonably short time. Aside from a 

 large collection of Nile fishes, there is ma- 

 terial preserved for researches in embryol- 

 ogy, electric organs, pseudo-electric organs, 

 neurology and Plankton. 



Tlie Coronary Vessels in the Hearts of Fishes. 



G. H. Parker and F. K. Davis. 



The muscular substance of the heart in 

 mammals receives its blood from a pair 

 of coronary arteries which connect with 

 coronary veins opening into the right 

 auricle. The inner surfaces of the four 

 chambers of the mammalian heart have 

 upon them openings which lead into vessels 

 connecting with the coronary capillaries, 

 and especially with the veins. These ves- 

 sels are the veins of Thebesius. Is there a 

 similar system of vessels in fishes? Cor- 

 onary arteries were identified in the com- 

 mon skate, the sand shark and the mud- 

 fish (Amia). In the skate they may come 

 from various combinations of the efierent 

 branchial arteries of the second to the fifth 

 gill cleft; in the sand shai'k, from combina- 

 tions reaching from the first to the fifth 



clefts ; in the mudfish, from the second bi-an- 

 chial arch. In these three species coronary 

 veins occur, all of which open into the 

 venous sinus. On inflating these, bubbling 

 was observed from the natural inner sur- 

 faces of the auricles and sometimes from 

 those of the ventricles. These fishes, there- 

 fore, have veins of Thebesius. 



Longitudinal Fission in Metridium margina- 

 tum. G. H. Parker. 

 Ten animals with double mouths were 

 studied. Two had each two mouths on one 

 oral disc, and the pedal ends of their 

 CBSophageal tubes were united. Eight had 

 each completely separate oral discs and 

 CESophageal tubes. In six the mouths were 

 monoglyphic ; in three one mouth was mon- 

 oglyphic and one diglyphic, and in one one 

 mouth was monoglyphic and one aglyphic. 

 There were about twice as many pairs of 

 complete mesenteries as in single mouthed 

 individuals. Double specimens are not the 

 result of fusion, for the two partial indi- 

 viduals are strikingly similar in color, etc., 

 a condition unlikely of occurrence in chance 

 combinations of so variable a species. They 

 may be monstrosities or dividing animals. 

 One specimen nearly divided was kept un- 

 der observation two months, but showed no 

 advance in the process. In good collecting 

 localities isolated pairs agreeing in color, 

 marking and sex may be found. This 

 evidence favors the view that M. margina- 

 tum reproduces, by longitudinal fission, a 

 process slowly accomplished, but it does not 

 exclude the possibility of some double speci- 

 mens being monstrosities. 



Additional Characters of Diplodocus. Henry 



F. OSBORN. 



This is one of the three types of herbivo- 

 I'ous Sauropoda or Cetiosauria, represented 

 by a very considerable portion of the skele- 

 ton of one individual found by Barnum 

 Brown and the writer in 1897. The scapula, 

 ilium, ischium and femur are associated with 



