664 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nesting Habits of Brook Lamprey.* — Messrs. R. T. Young and 

 L. J. Cole have made interesting observations on tlie behaviour of the 

 brook lamprey (Petromyzon wilderi) in moving stones for nest-building. 

 The lampreys seem to have little method, they seize a stone and carry 

 it straight ahead from the nest, in a few cases observed into the nest. 

 Two lampreys may move a stone conjointly. In a postscript, Prof. Gage 

 recalls his observation that this lamprey keeps to the brooks, attains its- 

 full size in the larval state, is never parasitic, remains in the sand during 

 the transformation-period (September to April), emerges in April to> 

 May, builds a nest, spawns, and disappears. 



Zoological Yearbook.f — We have received the Naples Jahresberichf 

 for 1899. It preserves the character it has had of recent years, con- 

 tinuing to exclude systematic papers. It is onco more ahead of the 

 Zoological Record in its date of publication. 



Tunicata. 



Branchial Sac in Ciona intestinalis. J— D. Damas has made a de- 

 tailed study of this structure in adult and larva, and has obtained results 

 in essence similar to those of Marc de Selys Longchamps § for Ascidiella. 

 In the adult the branchial sac shows six areas defined by five sinuses 

 Avhich differ from the other sinuses. Development shows that these areas 

 correspond to the protostigmata, the sinuses to the primitive sinuses 

 which ran between the protostigmata. Their persistence is to be ex- 

 plained as due to the simple primitive character of Ciona. Of the 

 intervening sinuses in the adult, it is found that each order contains 

 twice as many sinuses as the order below, thus there are six sinuses of 

 the second order, twelve of the third, and so on. Again, the area 

 between any two sinuses of one order is exactly halved by a sinus of 

 the next order, that is, a sinus of order three lies midway between two 

 sinuses of order two, and so on. These rules are true not only of the 

 transverse sinuses, but also of dorsal languets and branchial muscles, 

 and are a necessary consequence of the method of development. But 

 although the development follows uniform rules, it is not necessarily 

 synchronous in the six primitive areas ; for sinuses, languets, and muscles 

 begin to appear in the first of these before the fifth and sixth are com- 

 pletely formed, and this difference persists in the adult. The consequence 

 is that, although the six areas in the adult have their sinuses, &c. 

 arranged on the same plan in all cases, the number of sinuses is not 

 the same in each case. There appears to be no (known) limit to the 

 complexity which may be attained by the surface of the branchial sac. 



INVJSRTEBRATA. 



Plankton of the Elbe.|| — Herr B. Schorler finds the potamoplaukton 

 of the Elbe at Dresden to be distinguished by the scarcity of animal as 

 compared to vegetable life ; the latter is characterised by the great 

 abundance of diatoms, especially in the spring and autumn. Among 



* Amer. Nat., xxxiv. (1900) pp. 617-20. t Berlin, 1900, not continuously paged. 

 X Arch. Biol., xvii. (1900) pp. 1-H2 (2 pis.). § Cf. this Journal, ante, p. 36. 

 il Gravelius' Zeitschr. f. Gewasserkunde. ii. (1900) 27 pp. See Bot. Centralbl.. 

 Ixxxiii. (1900) p. 146. 



