March 27, 1903.] 



SCIENCE. 



483 



gest the possibility of its being a hybrid 

 between latipes (/^-female) and claviger 

 ^. (4) The OL- and /J-females represent 

 a new case of dimorphism setisu stricto in 

 L. latipes. Of these four hypotheses the 

 first and second may be rejected as too 

 improbable to be entertained. The true 

 meaning of the two forms of queens is 

 probably to be sought in the direction of 

 hybridism or of dimorphism sensu stricto. 

 Only further observation and experiment 

 can enable us to decide between these in- 

 teresting alternatives. 



Septal Sequence in Corals: J. E. Duerden, 

 University of North Carolina. 

 An account was given of the manner of 

 appearance of the septa in the "West Indian 

 coral, Siderastraea radians (Pallas), the 

 post-larval development of which has been 

 followed for four months. The results 

 were summarized as follows: 



1. The six members of the first cycle of 

 entosepta appear simultaneously, shortly 

 after fixation of the larva, situated within 

 the entocoeles of the first cycle of mesen- 

 teries. 



2. The members of the temporary second 

 cycle, consisting of six exosepta, are de- 

 veloped shortly after the primary cycle of 

 entosepta, within the primary exocceles. 

 The six septa arise simultaneously, or in 

 bilateral pairs in a dorso-ventral order. 

 Later they become bifurcated peripherally, 

 either by the direct extension of the orig- 

 inal septiun or by the production of sep- 

 arate fragments which subsequently fuse. 

 The bifurcations also appear in a dorso- 

 ventral order. 



3. The six members of the permanent 

 second cycle of entosepta arise within the 

 entocceles of the second cycle mesenteries, 

 after these have made their appearance. 

 The two right and left dorsal septa appear 

 first, then the two middle members, and, 

 at a much later period, the two ventral, 



thus exhibiting a decided dorso-ventrality. 

 In the end they become equal and fuse 

 with the central parts of the second cycle 

 of exosepta previously developed, which 

 now lose their individuality. 



4. The twelve members of the temporary 

 third cycle are situated within the exocoeles 

 between the primary and secondary pairs 

 of mesenteries, and represent the bifur- 

 cated extensions of the six primary exo- 

 septa. The original second cycle exosepta 

 thus become the third exocoelic cycle, their 

 place having been taken by the new second 

 cycle of entosepta (law of substitution). 



5. The later development of the septa in 

 buds proves that a new third cycle of septa 

 arises in a similar manner, on the appear- 

 ance of the third cycle mesenteries. New 

 entosepta appear within the entocoeles of 

 the third cycle mesenteries, and the bifur- 

 cations of the twelve third cycle exosepta 

 become the twenty-four exosepta of the 

 fourth cycle. 



6. Exosepta thus appear at each stage 

 in the growth of the corallum, alternating 

 in position and corresponding in number 

 with the entosepta. They never become 

 entosepta, but always constitute the outer- 

 most cycle; only the entosepta have any 

 ordinal significance. The adult radial 

 symmetry of the septa is secondary, being 

 derived from structures which appear bi- 

 laterally in a dorso-ventral order. 



The various stages in development were 

 illustrated by a series of wax models pre- 

 pared at the American Museum of Natural 

 History, New York. 



Iridescent Feathers : E. M. Strong, Haver- 



ford College. 



Iridescent feathers from the sides of the 

 neck of the common 'homer' pigeon appear 

 green when the sum of the angles of inci- 

 dence and reflection is less than 90°, and 

 purple when the sum is more than 90° 

 but less than 140°. The iridescence is 



