162 SUMMARY OF CURRENT RESEARCHES RELATING TO 



food-collecting- is effected by cilia on the papilla? and on the gills, and is 

 helped in some forms by transverse waving of the longitudinal bars. 

 The investigator's observations lend support to the view that the neural 

 gland in Ascidians is an organ for secreting mucus, which aids in the 

 collection of food-particles, and that the dorsal tubercle of Ascidians is 

 an organ for passing mucus on to the pharynx. The ciliation of the 

 gill-bars of Balanoglossus is essentially the same as that of Ampkioxus. 

 Hence the current of water through the body is doubtless produced by 

 the lateral cilia, and food-collecting is effected by the frontal cilia. 



The ciliation of the gill of Sohnomya closely resembles that of 

 Nucula ; the lateral cilia produce the main current ; the latero-frontal 

 and the frontal cilia collect food-particles, which the frontal cilia carry 

 to the ventral surface of the gill, whence they are conveyed to the 

 mouth by special transporting cilia. Numerous small ciliated knobs 

 occur on the ab-frontal face of the gill-lamellae, and serve to interlock 

 with their fellows on opposite leaflets. These ciliated knobs correspond 

 to the ciliated disks of the gill-filaments of other Lamellibranchs, such 

 as the mussel. Interlocking cilia occur on the edges of the upper and 

 lower leaflets of the gill, and serve to lock the gill to the inner wall of 

 the mantle, and thus to partition the mantle-cavity. The function of 

 the Lamellibranch gill is probably mainly that of a food-collecting 

 organ and water-pump, and except in Protobranchs it is probably not an 

 organ in which aeration of blood occurs. 



Tunicata. 



Protostigmata in Ascidians.* — A. G. Huntsman describes the 

 development of the primitive stigmata or gill-slits, which are elongated 

 dorso-ventrally and occur in a longitudinal series on each side of the 

 pharynx. The stigmata of the adult differ from these in being usually 

 very numerous, indefinite in number, and elongated antero-posteriorly. 



In Ciona there are to begin with two protostigmata of the first 

 order, arising from a division of the stigmatic primordium. The two 

 primaries produce four secondaries by division, and the first pair divide 

 into four tertiaries. The protostigmata are formed either by simple 

 sub-division or by modified sub-division, resulting in the intercalation 

 of new stigmata. Or there may be an intermediate method of sub- 

 division. In various ways, which are described, the protostigmata are 

 converted into the rows of definitive stigmata of the adult. The genesis 

 of the stigmata affords a proper basis for an understanding of the adult 

 pharynx and a serviceable aid in classification. 



Localization of Plastosomes in Ascidian Ovum.t— J. Duesberg 

 describes the unequal distribution of the fundamental substance, the 

 yolk-granules, and the plastosomes in the egg of Ciona intestinalis, and 

 regards the plastosomes in particular as the organ-forming substances. 

 He gives good figures and refers to other intances of localization 

 described by Conklin and others. 



* Proc. Roy. Soc, Series B, lxxxvi. (1913) pp. 440-53 (2 figs.), 

 t Verh. Anat. Ges., 1913, in Anat. Anzeig., xliv. (1913) Erganzung., pp. 3-13 

 (12 figs.). 



