ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 177 



Branchiostoma, Heteropleuron, and Asymmetron, namely B. pelaginim 

 Giinther, Heteropleuron maldivense Cooper, H. agassizii sp. n., H. par- 

 vum sp. n., Asymmetron orientate sp. n., and A. macrkaudatum sp. n. 

 — a somewhat remarkably rich material from three localities in the 

 Maldives. 



River Plankton.* — C. A. Kofoid has made an extensive study of the 

 plankton of the Illinois river for the years 1804 to IS!)'.). The period 

 of minimum productivity of plankton is in January and February ; this 

 is followed by rising productivity which reaches its maximum in April, 

 after which there is a gradual decline. Area and depth show little rela- 

 tion to plankton production, but fluctuations in hydrographic conditions, 

 temperature and light are important. Young waters from springs and 

 creeks have little plankton, but develop an abundant one when im- 

 pounded in backwater reservoirs. Submerged vegetation tends to 

 diminish the production of plankton. 



Plymouth Marine Invertebrate Fauna.f — A useful and interesting 

 list of the Plymouth marine invertebrate fauna has been compiled from 

 the records of the laboratory of the Marine Biological Association. The 

 various grounds are described, and the local distribution of species is re- 

 corded. 



Tunicata. 



Studies on Tunicates4 — D. Damas discusses in particular the 

 branchial region in Tunicates, the definition of the protostigma, the 

 number of protostigmata in various types (which he calls poly-, hexa-, 

 tetra-, di-, and mono-prostigmata), the development of the branchial 

 apparatus in these types, and so on. He holds firmly to the proposition 

 that Tunicata have but one pair of branchial clefts, in the strict sense. 

 The paper also includes a discussion of the segmentation of the tail of 

 Appendicularians. In Oikopleura dioica there are ten muscle-plates, 

 each innervated by a motor nerve, and apparently representing true 

 segments. Finally, the author has some interesting notes on the struc- 

 ture of the larva of Distaplia magnilarva. 



Physiological Polarisation in Ascidian Heart. § — F. W. Bancroft 

 and C. 0. Esterly describe certain experiments upon the heart of Ciona 

 intestinalis, from which they conclude that not only does the direction of 

 the Contractions remain fixed, while a part of the heart is connected with 

 only one of its ends, but that in some way a change is effected in the 

 heart tissue, so that the direction of the contractions still remains fixed 

 after the part has been isolated from the end which was instrumental in 

 producing the fixation. The heart tissue becomes physiologically polar- 

 ised by being left in contact for a while with only one end of the heart. 



* Bull. Illinois State Lab. Nat. Hist., vii. pp. 95-629 (50 pis.). See Amer. 

 Nat., xxxviii. (1904) p. 397. 



t Journ. Marine Biol. Assoc, vii. (1904) pp. 155-298 (1 chart). 



X Arch. Biol., xx. (1904) pp. 745-833 (4 pis.). 



§ Univ. California Publications, i. (1903) pp. 105-14. 



