296 SUMMARY OF CURRENT RESEARCHES RELATING TO 



nificus vies with the majority of Cepkalaspis species. The head-shield is 

 39 rum. in length by 88 mm. in width. 



Thyroid of Myxine.* — J. Schaffer refers to a recent statement by 

 F. J. Cole that "the thyroid of Myxinoids has not hitherto been 

 described." It was briefly described by W. Miiller in 1871. Schaffer 

 notes that he re-discovered it in 1896, but refrained from publishing 

 a note when he found Midler's description. A peculiar glandular 

 structure occurs between the branchial pouches in the form of single or 

 grouped spherical or oval vesicles, the walls of which are formed from a 

 single layer of cubical or prismatic epithelium. They occur from the 

 ventral surface of the gullet to the dorsal convexity of the branchial 

 artery and its main branches, and are found from the first to the last 

 pouch. Their development must be known before a final decision can 

 be given, but their median unpaired occurrence and their minute structure 

 (e.g. intracellular inclusions like similar bodies in the thyroid of man) 

 point to their being thyroid (not thymus) elements. 



Natural History Notes from St. Andrews.! — W. C. M'Intosh 

 describes a very young stage (:>5 mm.) of Phycis blennoides (captured off 

 Messina), the female Heteronereid of Nereis pelagica, specimens of 

 bifid Nemerteans, and gives some notes on Amphiporus hastatus M'L, as 

 afforded by a very fine example recently captured at St. Andrews. 



Tunicata. 



Two remarkable Ascidians.J — 0. Ph. Sluiter makes a preliminary 

 note on two remarkable forms collected by the Siboga Expedition. The 

 first, Dicopia fimbriate g. et sp. n., is a simple Ascidian, much com- 

 pressed from in front backwards ; the broad cleft-like branchial aperture 

 is turned upwards, and is surrounded dorsally and ventrally by two very 

 large lobes, into which the muscular layer is continued ; the atrial open- 

 ing is quadrangular and hidden under the large dorsal oral lobe ; the 

 under surface of the body bears a wreath of long thin attaching threads ; 

 there are no proper stigmata. The second, Hexaerobylus psammatodes 

 g. et sp. n., is a simple Ascidian with two apertures almost diametrically 

 opposite one another at the ends of an almost cylindrical body ; the 

 branchial aperture is surrounded by a duplicature of the mantle forming 

 six large teat-like prolongations ; there are no stigmata : the gonads are 

 paired. 



Development of Diplosomidae.§ — Antoine Pizon deals with the 

 formation of the colonies after the embryonic period, that is, after the 

 fixation of the larvas. He describes the transformation of the oozooid 

 into a bithoracic ascidiozooid, the transformation of the bithoracic ascidi- 

 ozooid into a monothoracic ascidiozooid, the transformation of the mono- 

 thoracic ascidiozooid into a bithoracic and biventric ascidiozooid, the 

 doubling of the bithoracic and bigastric ascidiozooid into two mono- 

 thoracic ascidiozooids with exchange of abdominal viscera, and so on — 



* Auat. Anzeig., xxviii. (1906) pp. 65-73 (6 figs.). 



+ Ann Nat. Hist., xcvii. (1906) pp. 66-81 (2 pis.). 



X Tijdschrift Nederland. Dierk. Ver., ix. (1905) pp. 325-7 (2 figs.). 



§ Arch. Zool. Exper., iv. (1905) pp. 1-68 (8 pis.). 



