438 



SCIENCE 



[N. S. Vol. XLI. No. 1055 



4. The chief objection to the homology main- 

 tained by Van Wijhe is the fact that the anterior 

 endodermie diverticula of Amphioxus are homol- 

 ogous — not with the pre-mandibular head cavities 

 of Elasmobranehs as assumed by Van Wijhe — but 

 with the "anterior" head cavities. The homol- 

 ogues of the pre-mandibular cavities of Elasmo- 

 branehs (the first permanent myotomes) are the 

 first permanent myotomes of Amphioxus. 



Amphioxus does not eat with his left ear. The 

 homologue of the left spiracle is the first transient 

 gill cleft of Amphioxus. The mouth of Amphi- 

 oxus, however, is not homologous with the mouth of 

 Craniotes. If it is homologous with any organ 

 of the Craniotes, that organ is the hypophysis. 



Embryology 

 Internal Factors Producing the Swarming of the 



Atlantic Falolo: Aaron L. Treadwell. 



Previous explanations of the swarming of anne- 

 lids have been based on the influence of the ex- 

 ternal factors such as light, tidal pressure, etc. At 

 the Carnegie Laboratory in the Dry Tortugas I 

 was able with the cooperation of Dr. Tashiro to 

 test the hypothesis that an internal factor co- 

 operates in producing this effect. Since all the 

 eggs of the Atlantic palolo are laid at one defi- 

 nite time, it is possible to test the eggs at any de- 

 sired interval before the time when they would 

 normally be laid. Testing with his biometer, Dr. 

 Tashiro found that five days before laying each 

 egg gave off 0.000,000,07 grams of CO, per min- 

 ute; two days before laying 0.000,000,083 grams, 

 while eggs taken from the body of a swarming fe- 

 male were eliminating 0.000,000,13 grams per 

 minute. All eggs were taken from the body with- 

 out mixture with sea water. This indicates an in- 

 crease in metabolic activity as the time of swarm- 

 ing approaches, and the conclusion follows that 

 this furnishes an internal stimulus of importance 

 in producing the swarm. Probably a similar stim- 

 ulus is operative in ordinary egg laying. 



Are the Taste-huds of Elasmoiranchs Endodermal 



in Origin?: Margaret H. Cook. (Introduced 



by H. V. Neal.) 



An attempt to determine the origin, whether 

 ectodermal or endodermal, of taste-buds in 

 Squalus acanthias. A study was made of sections 

 of embryos of 7 to 80 mm. supplemented by dis- 

 sections of "pup" and adult stages. 



Taste-buds in this species are limited to the re- 

 gion of the pharynx, which in all stages of onto- 

 genesis is lined with endoderm. No marked en- 



croachment of the ectoderm is perceptible even in 

 the mouth region. 



Scales similar to those which characterize the 

 outer skin arise in late stages of ontogenesis in 

 both the floor and roof of the pharynx. Thus two 

 kinds of organs usually classed as ectodermal, viz., 

 taste-buds and placoid scales, appear to arise from 

 the endoderm of the pharynx of Squalus acanthias. 

 To assert that the pharyngeal taste-buds and scales 

 of Squalus are ectodermal would necessitate the 

 assumption that the endodermie lining of the 

 pharynx completely disappears during ontogeny 

 and is replaced by ectoderm. Evidence of such 

 substitution is wholly lacking. 



These results extend to the Elasmobranehs the 

 conclusion of Johnston ( '98 and '10) that the 

 taste-buds of Teleosts and Amphibia are derived 

 from endoderm. They also add to the structures 

 derived from the endoderm the pharyngeal scales 

 which have hitherto been assumed to be ectoder- 

 mal, and thus add another exception to the law of 

 the specificity of the germ-layers. 



On the Larval and Post-larval Development of the 

 Coral, Agaricia Fragilis, Dana: J. W. Mavoe. 

 (With lantern.) (Introduced by E. L. Mark.) 



Tissue and Organ; Their Bdles in Morphogenesis : 



Herbert W. Eand. 



Definiteness of form is the essential characteris- 

 tic of an organ. Tissue is without form. Our at- 

 tempt to discover the factors immediately re- 

 sponsible for the form of an organism will be 

 furthered if we clearly distinguish the parts 

 played by organic units of the several grades. 

 How far does a given formative event depend 

 upon cells acting as uncoordinated individuals, 

 how far does it depend upon a system of cells co- 

 ordinated into a tissue, and how far does it ex- 

 hibit the impress of organization higher than 

 that of tissue? 



In the wound-closing activities of tentacles of 

 actinians, cells, as such, play a minor and prob- 

 ably unessential part. The definitive structural 

 closure is an autonomous tissue process. Accom- 

 panying activities of the neuro-muscular complex 

 afford temporary protection and favor the carry- 

 ing out of the tissue process. In these activities 

 and in other reactions of the neuro-muscular 

 complex, we observe polarity and a variety of 

 definite relations to the form of the organism. 

 These bespeak for the neuro-muscular complex a 

 degree of organization higher than that of mere 

 tissue, probably corresponding to the organism as 

 a whole. 



