762 SUMMARY OF CURRENT RESEARCHES RELATING TO 



variations. In connexion with Cephalothrix linearis he contributes 

 welcome information in regard to the circulation. There is a definite 

 circulation in the lateral vessels, occasioned by a series of contractile 

 waves alternately postero-anterior and antero-posterior ; this is not due 

 to contractions of the body-wall, nor to movements of the body as a 

 whole; it would seem necessary, therefore, to assume the presence of 

 muscular tissue in the walls of the vessels. 



The species Cephalothrix rufifrons and C. bioadata are only colour 

 varieties of G. linearis, and the unification of Lineus gesserensis and 

 L. sanguineus is confirmed. 



Experiments on Ova of Cerebratulus.* — Max Withrow Morse finds 

 that reagents, such as saponin, oxalic, hydrochloric, and tartaric acids, 

 which were used successfully to induce maturation, would not cause 

 segmentation to proceed. 



It was found, however, that if all trace of these reagents was washed 

 off, and the eggs placed in a C0 2 sea-water solution, with a concentra- 

 tion of about o"l9 grm. to 100 grm. sea-water, segmentation proceeded, 

 though development did not continue beyond the later segmentation 

 stages. 



Loeb and others have observed, in other cases, this antagonistic 

 action of reagents which induce maturation and those which induce 

 segmentation. " In such cases, as in the present one, the reactions are 

 not reversible ; C0 2 will not cause maturation." 



Incertae Sedis. 



New Mediterranean Bryozoa.j — Louis Calvet describes Idmonea 

 arborea sp.n., a vigorously growing form, ramifying dichotomously ; 

 and Amathia pruvoti sp.n., which is intermediate between A. lendigera 

 and A. semi-convoluta. 



Barentsia benedeni in British Waters. J — James Ritchie describes 

 specimens of this endoproctan Polyzoon which was found at Hull 

 growing on the surface of Membranipora on the dock timbers. The 

 Hull specimens seem to take a place intermediate between Barentsia 

 benedeni (Foettinger), known only from Ostend, and B. gracilis (Sars), 

 which occurs on Belgian and English coasts. The salient characters of 

 the specimens are : Stem composed of up to 8 well-defined, robust 

 internodes (3 or 4 being most common), from which buds may arise ; 

 no pores in chitinous portions of internodes ; no granular masses in 

 internodes ; calyx relatively small, with transparent, colourless walls ; 

 tentacles 10 to 14, colourless ; brain trapezoid in transverse sections. 



Consideration of the variations of this and of related species leads 

 the author to the following conclusions : — 



1. Arthropodaria Ehlers is synonymous with Gonypodaria Ehlers, 

 and both are included in Barentsia. 



2. Gonypodaria nodosa (Lomas) is synonymous with Barentsia 

 gracilis. 



* Science, xxxiii. (1911) p. 388. 



f Arch. Zool. Exper., viii. (1911) Notes et Revue, No. 3, pp. lvii.-lxi. (2 figs.). 



% Trans. R. Soc. Edinburgh, xlvii. (1911) pp. 835-48 (1 pi.). 



