312 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



Tunicata. 



'Tadpole Larva of Amaroucium. — Caswell Grave {Journ. Exper, 

 ZooL, 11)20, 30, 239-57, 4 figs.). A study of the activities and 

 reactions of the larva of A. 2)ellucidutn (Leidj) form constellat if m Verrill. 

 The body is in constant clockwise rotation on its long axis as it is 

 propelled through the water by the tail. The rotation is due either to 

 the asymmetrical form of the body, or to a torsion of the tail during its 

 strokes, or to both. Immediately after liberation they react positively 

 t>o light ; during the later and greater part of their free-swimming life 

 they react negatively. At first they remain at or near the surface ; later 

 at or near the bottom. There may be a changing response to gravity ; 

 but the response to gravity is aided by the presence of directive rays of 

 Ught. The viscid contents of the glandular ends of the adhesive 

 papillae are extruded on the outer surface of the tunic toward the close 

 of the free-swimming period, and the initial attachment of the tadpole 

 is due to one of these droplets coming accidentally into contact with the 

 surface of a foreign body. The free-swimming period lasts from ten 

 minutes to two hours. J. A. T. 



INVERTEBRATA. 



MoUusca. 

 a. Cephalopoda. 



Histolog'y of " Branchial Hearts " of Sepia. — E. Fernandez 

 Galiano (Boll. Soc. Espan. Hist. Nat., 1919, 19, 853-Sl, 1 pi., 10 figs.). 

 These enigmatical organs, situated at the base of the gills, are very 

 vascular and likewise glandular. An account is given of their external 

 epithelium (showing many intercellular bridges), their muscle fibres, and 

 connective tissue network. The appendix to the so-called " l)ranchial 

 heart" is also described. The cortical part comprises an epithelium, 

 a connective stroma, blood vessels, muscle-fibres and free cells. The 

 author inclines to regard the branchial hearts and their appendices as in 

 part pulsatile, but mainly excretory. J. A. T. 



Ammonite Siphuncle.— A. E. Trueman {Geol. ALag., 1920, 57, 

 26-32, 2 figs.). The siphuncular tube or envelope (around the 

 membranous siphuncle jjroper) is not continuous in Anmionites through 

 all the chambers to the body chamber. In some cases the envelope did 

 not extend through the ten chambers preceding the living chamber. 

 This is seen in young as well as in old specimens, though the number 

 of chambers in wliicli there is no envelope apparently increases with the 

 age of the individual. Tlie autlior inclines to accept the suggestion 

 of Foord and Woodward that the siphuncle was of more importance 

 in the young animal, perhaps then serving for aitachment, but that later 

 on this function was performed V)y the shell muscles. It is not unlikely 

 also that the siphuncle was of much greater importance in the early 

 stages of Cephalopod evolution than it is in Mesozoic and recent forms. 

 The tendency for the secretion of the sipliuncular envelope in Ammonites 

 to lag behind shell-growth suggests that the vahie of the siphuncle may 

 at least have been declining:. J. A. T. 



