174 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the warmer season of the year ; but much less widely separated in that 

 part built up during the colder season. Thus the annual rings enable 

 one to infer the age of the fish, much as the rings in the wood of a tree 

 stem inform us as to the age of the tree. Hoffbauer has recently (1899) 

 reached similar conclusions in regard to the scales of carp. 



Vascular System of Bdellostoma dombeyi.* — C. M. Jackson gives 

 a careful and very welcome description of the vascular system in this 

 Myxinoid. We cannot within our space follow his anatomical account, 

 but we cite his conclusions as to the primitive and the secondarily 

 acquired characters. 



The primitive characters are : — persistent pericardio-peritoneal fora- 

 men, simple tubular heart, the large number (up to 14) of functional 

 branchial vessels, the origin of the carotid arteries from a lateral com- 

 missural vessel on each side connecting all the efferent branchial arteries,, 

 the complete sub-chordal aorta (dorsal aorta) extending forwards into the 

 head region, the segmental arrangement of the somatic and renal arteries 

 and veins, the frequent anastomosis between the posterior cardinal veins, 

 the persistent sub-intestinal vein which does not join the portal system, 

 the presence of an inferior jugular vein, and the well-developed portal 

 heart which occurs nowhere else among Vertebrates except in the closely 

 related Myxine. 



The characters secondarily acquired are : — the asymmetry of the 

 venous system, the distribution of branchial vessels to gill-slits instead 

 of to gill-arches, the extension of the portal system into the territory of 

 the right anterior cardinal vein, the connection of the caudal vein with 

 the posterior cardinals, and the valvular character of the portal heart. 



Fauna of Exe Estuary.f — Dr. E. J. Allen and Mr. R. A. Todd give 

 a valuable account of the fauna of the Exe estuary, similar to that pre- 

 viously given for the Salcombe estuary. A comparison of two faunas is 

 interesting in many respects. That of the Exe estuary is much more 

 limited, and this seems to a large extent due to the following causes : — 

 The banks uncovered in the Exmouth estuary are left dry for a very long 

 time between the two tides, and in most parts of the estuary there is 

 little difference in the area uncovered by the spring and neap tides ; 

 the great strength of the tidal stream involves a scouring of the banks ; 

 a large quantity of fresh water enters the estuary. In an appended 

 paper J R. H. Worth reports on the Foraminifera, of which about twenty 

 species are common. 



INVERTEBRATA. 



Autotomy in Marine Invertebrates. § — Dr. Emanuel Riggenbach 

 gives a preliminary account of some observations on self-mutilation 

 made on common marine forms. In the Echinoderm Ophioderma longi- 

 cauda, the mere removal of the natural element is sufficient to induce 

 movements of the arms, so vigorous as to lead to separation of parts of 

 these. Fragments break off in rapid succession from the extremities 



* Journ. Cincinnati Soc. Nat. Hist., xx. (1901) pp. 13-47 (3 pis. and 10 figs.). 



t Journ. Mar. Biol. Ass., vi. (1902) pp. 295-335 (1 map). 



j Tom. cit., pp. 33G-43. § Zool. Anzeig., xxiv. (1901) pp. 587-93 (6 figs.). 



