152 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Abortive Embryo of Salamandra atra.* — H. Hirzel has studied 

 an abortive accessory embryo, which shows a monstrous dilatation of the 

 body-wall. The nervous system is normal or nearly so, and the 

 ectoderm ic products generally are less divergent than the mesodermic 

 and endodermic organs, such as the rudimentary and peculiar repre- 

 sentatives of heart and lungs. 



Development of Hyobranchial Skeleton in Salamandra atra and 

 Triton alpestris.j — Helena Tarapani gives a caref nl account of the 

 development of the hyoid and branchial arches in the larvre of these 

 Urodela, and of the retrogressive changes and new formations which 

 lead from the larval skeleton to the definite support of the tongue. 

 Some beautiful reconstructions are photographed. 



Spermatogenesis in Alytes obstetricans.J — 1°. A. Janssens and 

 J. Willems describe (a) the " somatic kinesis " of the mother sperm-cells, 

 the twin chromosomes, and the behaviour of the nucleoli ; (b) the 

 maturation kineses, the zygosomes, the amphitajne stage, the pachytene 

 stage with dyads, the dyads in a ring, and so on. 



Hypochord in Skate Embryos. §— W. T. (Jibson discusses this 

 structure— the sub-notochordal rod of many embryologists — as it appears 

 in embryos of Raid bath. It is practically co-extensive with the em- 

 brvonic ?ut and with the notochord until the formation of the latter 

 ceases posteriorly. It is derived from the chorda-hypoblast, and it never 

 loses touch with the notochord except within the last stages of degenera- 

 tion. It ends its existence within the embryonic period, disappearing 

 long before the notochord reaches its maximum size. It is confined 

 to the Ichthyopsida, and is probably in some way "useful to the 

 notochord." 



The author also discusses the epibranchial groove. Vestiges of it 

 occur in embryos of reptiles and birds, and of the skate ; the theory is 

 suggested that the air-bladder may be derived from it. 



Metameres of Petromyzon.||— B. Hatschek finds that the paired 

 mesoderm bands exhibit a thorough-going segmentation, hyposomatic 

 a,s well as episomatic, resulting in primitive segments like those of the 

 lancelet. At a stage when the primitive segments are defined, and so 

 far differentiated that their parachordal myoblasts extend through the 

 entire length of the segments, the first mandibular segment (mesodermic 

 acromerite) is still in process of being constricted off from the endo- 

 derm. The formation of myoblasts is at this stage still lagging in the 

 second, third, and fourth segments. The archencephalon (first and 

 second primary vesicles) corresponds in its extent to the mandibular 

 segment, and belongs to the acromerite. The first visceral pouch is 

 intersegmental, its anterior wall belonging to the acromerite, its 

 posterior wall to the second segment. 



* Jenaische Zeitschr. Naturw., xlv. (1909) pp. 1-56 (3 pis.). 



t Tom. cit., pp. 57-110 (6 pis.). 



X La Cellule, xxv. (1909) pp. 151-78 (2 pis.). 



§ Anat. Anzeig, xxxv. (1909) pp. 407-28 (13 figs.). 



|| Morphea. Jahrb., xl. (1909; pp. 480-99 (2 pis. aud 1 fig.). 



