418 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Incertae Sedis. 



Body Cavities and Nephridia of Actinotrocha.* — R. P. Cowles 

 has found in two Actinotrochge from Beaufort, North Carolina, that 

 there is au incomplete mesentery between the preoral lobe and the 

 collar cavities, and a complete one between the collar and trunk cavities. 

 The trunk cavity contains a ventral mesentery, and in one species, 

 indications of a dorsal mesentery ; but there is no sign of a dorsal 

 mesentery, such as Masterman describes for the collar cavity. The 

 mesoderm was not found to arise from archenteric diverticula. The 

 anterior and lateral borders of the blastopore are most active in giving 

 rise to mesoderm cells, which in the gastrula stage form a definite sac. 

 This sac anteriorly becomes the lining of the preoral lobe, while its 

 posterior wall becomes the lobe collar mesentery. The preoral lobe and 

 the lobe collar mesentery are lost during metamorphosis ; the collar 

 cavity and its lining become the ring vessel of the adult ; the cavity 

 of the mesodermal sac between the mesodermal lining of the collar 

 cavity and the ventral ectoderm becomes the supra-septal cavity of the 

 adult ; the trunk cavity, including the cavity of the ventral pouch, is 

 transformed into the infra-septal body cavity, and the mesentery between 

 the collar and trunk cavities becomes the transverse septum of the adult. 

 The author's observations on the nephridia confirm the work of Goodrich 

 in nearly every detail. 



Regeneration in Phoronis Miilleri.f — E. Schultz discusses in a 

 third paper on regeneration phenomena the results of his experiments 

 on Phoronis. The animals were cut by means of scissors at various 

 levels, — through the tube, and above it with head expanded. In every 

 case, whether severed only through the tentacles, through the first part 

 of the oesophagus, at a point where spontaneous breaking away of head 

 goes on, or still lower down, normal animals resulted. The notable fact 

 here brought out, that the most protected parts within the tube, — not 

 likely in the ordinary course to suffer injury, — regenerated as well as 

 the exposed portions, suggests that regeneration has not arisen through 

 natural selection, but is a primary peculiarity of living substance. 



Ptychodera flava funafutica.^ — J- W. Spengel gives an account of 

 a form of Ptychodera flava from Funafuti (Ellice group), and emphasises 

 especially the differences between it and Pt. fl. caledoniensis of Willey 

 and Pt.fl. laysanica. 



Development of Blood- Vessels and Blood-Corpuscles in the Actino- 

 trocha Larva.§ — R. P. Cowles discusses this difficult question. The 

 Actinotrocha, which has just completed its metamorphosis, has only one 

 ring-vessel (larval collar-cavity), but the young Phoronis, when it is 

 twelve hours old, possesses both the recipient and distributing vessels. 

 These, the author believes, arise by the fusion of the walls of the single 

 ring-vessel in the metamorphosing Actinotrocha, and by the subsequent 



* Johns Hopkins University Circular, 1904, No. 2, pp. 28-37. 

 t Zeitsclir. wiss. Zool., lxxv. (1903) pp. 391-120 (2 pis.). 

 X Zool. Jahrb., xx. (1904) pp. 1-18 (2 pis.). 

 § Zool. Anzeig., xxvii. (1904) pp. 598-906 (7 figs.). 



