Mat 10, 1907] 



SCIENCE 



727 



the eaves of the alligators, vary consider- 

 ably in size, and consist of a very compact 

 mass of damp, decaying vegetation. They 

 probably serve more as a means of keep- 

 ing the eggs moist and at a constant tem- 

 perature than as a means of heating them. 

 The average number of eggs in a single 

 nest is about thirty, forty-eight being the 

 greatest number found in one nest. The 

 eggs are so closely packed in the nest that 

 it seems hardly possible that the young 

 alligators, on hatching, should be able to 

 dig their way out; it is possible that the 

 female who laid the eggs may hear the 

 noise made by the young before hatching 

 and may dig them out of the nest before 

 they suffocate. The period of incubation 

 is probably about eight weeks, and some- 

 times is found to have begun before the 

 eggs are laid, so that eggs taken directly 

 from the oviducts may contain well ad- 

 vanced embryos. There is considerable 

 variation in the size of the eggs, the varia- 

 tion in long diameter being greater than 

 that in short diameter. The average long 

 diameter of the four hundred eggs meas- 

 ured was 73.742 mm. The average short 

 diameter was 42.588 mm. 



An Electric Wax-cutter for Use in Recon- 

 structions: Edwaed L. Maek, Zoological 

 Laboratory, Harvard University. 

 The wax-cutter is made by heating a 

 platinum wire about 0.4 mm. in diameter 

 by means of an electric current regulated 

 by a rheostat consisting of ordinary elec- 

 tric lamps of different candle power and 

 arranged in multiple. To give the wire 

 alternating motion parallel to its length, it 

 is stretched in a frame made of a bent 

 steel rod, one portion of which is sub- 

 stituted for the 'needle-bar' of an ordi- 

 nary household sewing machine. The 

 melted wax is withdrawn through a copper 

 tube— kept hot by passing through a small 



hot- water tank— attached to a suction 

 pump of the Bunsen type. 



The apparatus is fully described and 

 illustrated in a number of the Proceed- 

 ings of the American Academy of Arts Eind 

 Sciences published in March. 



The Microscopic Structure of the Stigmal 

 Plates of the Tick Genus Dermacentor: 

 C. W. Stiles, "Washington, D. C. 



The Circulatory System in Nereis: H. R. 



LiKviLLE, New York. 



The general plan of the circulatory sys- 

 tem and the circulation in Nereis, as ob- 

 served in living individuals, is a median 

 dorsal vessel in which the blood flows an- 

 teriorly as the result of peristaltic waves 

 of contraction in the wall of the vessel, and 

 a larger median ventral vessel in which 

 blood flows posteriorly without contrac- 

 tion of the wall. Anteriorly the dorsal 

 vessel branches at the cephalic plate into 

 four vessels, and the blood is carried down- 

 ward and posteriorly through a set of 

 capillaries in the region of the pharynx to 

 the ventral vessel. Posteriorly the last 

 three somites of the trunk have single pairs 

 of blood vessels which carry blood upward 

 into the dorsal vessel. Beginning at the 

 eleventh trunk somite and extending to the 

 fourth somite from the posterior end, there 

 is a complicated arrangement of lateral 

 vessels and capillaries. At a point near 

 the anterior end of each intermediate 

 somite a pair of 'hearts' lying close to the 

 intestine carry blood downward in peris- 

 talic waves, to a pair of short vessels which 

 connect with the ventral vessel. A portion 

 of the blood carried by the hearts passes 

 into these short connecting vessels, and then 

 into the ventral vessel or out into another 

 pair of blood-vessels that start from the 

 ventral ends of the short connecting vessels 

 and extend to the nephridia in the ventral 

 rami of the parapodia. The remainder of 

 the blood from the hearts goes into a pair 



