5 1U SUMMARY OF CURRENT RESEARCHES RELATING TO 



which is due to an accumulation of yolk in this region of the digestive 

 tract. There are also two ventral primordia of the pancreas, and their 

 history is traced. The liver arises as an isolated organ at the expense of 

 a ventral zone of epithelium on the vitelline intestine, and it is con- 

 stricted off dorsally, not ventrally, which again is due to the position of 

 the yolk in gut. In regard to the spleen, the author confirms the con- 

 clusions of Piper and Laguesse, that this organ arises in a mesen- 

 chymatous area quite independent of the pancreas. 



Development of the Swim-Bladder.* — Fanny Moser has investigated 

 the early stages in several fishes, e.g. Gyprinus, Salmo, Gasterosteus. 

 Her conclusions are in favour of a relationship between lungs and air- 

 bladder. She noted a double movement of the intestine, a displacement 

 from the side (from left in carp, Rhodeus, etc., and from the right in 

 salmon) towards the middle line under the notochord, and then a 

 twisting of the intestine upon its own axis, through which the origin of 

 the ductus pneumaticus is shifted. In some cases it passes from the 

 right side to the dorsal and even towards the left, in others from the 

 dorsal side towards the left. The author considers the shifting per- 

 manent and not due to the changes in the yolk mass during absorption. 

 In the trout the twisting affects to some extent the air-bladder also ; in 

 Rhodeus this is not the case. If a movement of the air-bladder round 

 is possible, the hypothesis of a phylogenetic shifting gains in probability. 

 One has only to think of the twisting of the bladder in the trout as 

 continued ; a side position would be reached as occurs in the Erythrina? ; 

 continued further it would end in being ventral, as in Polypterus. 

 It is more probable that the bladder and ductus followed the move- 

 ment of the gut than that an independent twisting of the ductus took 

 place around a fixed gut. The absence of bladder in certain forms the 

 author regards as secondary. 



Degeneration in Relation to Regeneration.! — E. Schultz kept 

 Dendroccdum lacteum throughout the winter without food. In this 

 time — six months — they had become reduced to one-tenth of their 

 original size. This reduction was due to falling away of a great number 

 of cells ; the size of remaining cells being unaltered. In four to six 

 months a part of the organs had quite disappeared. Thus, of the 

 copulatory organs only a hollow remained, which afterwards also 

 disappeared, so that at last he found only a group of cells which was 

 specialised to the extent that it could re-form the same organ. The 

 vasa efferentia disappeared, also the oviducts ; only the sexual organs 

 themselves remained unattacked, in spite of the fact that the sex products 

 do not mature during starvation. The pigment cells of the eyes fall 

 away and the pigment disappears. The gut epithelium partly degener- 

 ates ; a few cells assume an embryonic character. Here there is a 

 whole series of retrogressive processes, which go through the stages 

 followed in regeneration,^ but in reverse order. 



* Arch. Mikr. Anat., Band lxiii. (1901) pp. 532-74 (4 pis.), 

 t Biol. Centralis., xxiv. (1904) pp. 310-17. 

 X Zeitsckr. wise. Zool., Ixxii. (1902). 



