866 



SCIENCE. 



[N. S. Vol. XXI. Xo. 544. 



just behind the degenerating embrj^onic 

 pharynx, which is, therefore, located on 

 the future ventral part of the body as the 

 spherical embryo becomes flattened. This 

 confirjns Ijima's ('84) description of the 

 orientation in Denclroccelum lacteum. In 

 B. maculata the point at which the degen- 

 erating embryonic pharynx is last seen is 

 on the dorso-posterior surface. 



The Arrangement of the Mesenteries in the 

 Cerianthidce. J. Playfair McMurrich, 

 University of Michigan. 

 In 1892 Faurot observed that the mesen- 

 teries of Cerianthus membranaceus were 

 arranged in groups of four, each quartet 

 consisting of a longer and a shorter fertile 

 mesentery alternating with a longer and a 

 shorter sterile one, and his observation was 

 subsequently confirmed by van Beneden 

 for C. Lloydii. Both authors regarded 

 the quartets as beginning with the fourth 

 mesentery on each side of the mid-siphon- 

 oglyphic line. The study of the develop- 

 ment of the cerianthid mesenteries has 

 shown, however, that the first four mesen- 

 teries on either side of the mid-siphon- 

 oglyphic line constitute a group distinct 

 from the others and are comparable to the 

 eight protocnemes of the other groups of 

 Anthozoa. 



Among the 'Siboga' actinians is a 

 species from Amboina, probably C. elon- 

 gatus Kwietn. In this form there is on 

 either side of the mid-siphonoglyphic line 

 the usual short sterile directive mesentery, 

 then follow two additional sterile mesen- 

 teries, and then a long fertile mesentery 

 which extends almost to the aboral pole of 

 the body. This last is apparently the so- 

 called continuous mesentery, and the inter- 

 est of it lies in the fact that it is the fourth 

 mesentery and not the second, as in all 

 other species that have been examined. 

 This departure, which occurs in all the in- 

 dividuals of the species examined, corrobo- 



rates the view based on the developmental 

 history that the four mesenteries on either 

 side of the mid-siphonoglyphic line consti- 

 tute a group apart from the rest, and that 

 the quartets should be regarded as begin- 

 ning with the fifth mesenteries. 



An Improved Form of Reconstruction Ap- 

 paratus: Thomas G. Lee, Laboratory 

 of Histology and Embryology, University 

 of Minnesota. 



Doctor Lee presented a very satisfactory 

 form of reconstruction apparatus, which he 

 had designed and which is an improvement 

 over the models now in use. It consists of 

 a cast-iron bed plate 8^ cm. (3^ inches) 

 thick at sides, and 4 J cm. (2 inches) thick in 

 the middle. The top measures 23 x 30 cm. 

 (9x12 inches), and has been accurately 

 planed and polished, giving an area of 690 

 sq. cm. (108 sq. in.). The side pieces, by 

 which the thickness of the wax plate is de- 

 termined, are moved up an inclined plane 

 which is rigidly fastened to the bed plate in 

 a manner similar to the movement of the 

 object holder in a Thoma microtome. 

 All parts of the top of each side piece 

 are thus always in the same plane. The 

 side piece is moved up and down by a 

 large and accurately made screw at the 

 rear of the apparatus. After adjust- 

 ment the side pieces can be firmly fixed 

 in place by two set screws by means of 

 a small wrench. A metal scale is placed 

 on each side piece, so that any thickness of 

 wax plate can be made from i mm. up to 1 

 cm. at I mm. intervals. Thus plates of ^, 

 1, li, 2, 2i mm., etc., can be made. Pro- 

 jecting from the bed block are two metal 

 strips with a depression to hold the roller 

 when not in use. This whole apparatus 

 weighs about 67 pounds, and is quite rigid. 



The roller is of polished steel 30 cm. (12 

 inches) long by 6 cm. (2| inches) diameter, 

 with a steel rod projecting at each end and 

 covered by a movable wooden handle. This 



