4 AUGUSTA ÄRNBÄCK-CHRISTIE-LINDE, NORTHERN AND ARCTIC INVERTEBRATES. 



in his famous work entitled »la Blastogénése chez les Botryllidés», arrived, in the 

 main, at the same results as Della Valle. 



Herdman l lias given anatomical descriptions of several Botryllid species, but 

 our knowledge of the reproductive organs has not been essentially furthered by them. 

 The result he arrived at may be expressed in his generic diagnosis, viz. : »Reproduc- 

 tive organs placed on both sides of the body near the posterior end». 



The inconclusive statements given on this point in Bronn's Tierreich by Seeliger 

 would seem in certain respects to be in agreement with those given by Della Valle. 



We owe excellent descriptions of the group in question to Van Name 2 and 

 Michaelsen 3 of a date as recent as the year 1921. The problem, however, of 

 the genital organs still remains unsolved, though, according to the last-mentioned 

 author, many years had been devoted to the study of those animals. 



The Botryllids here examined ha ve been divided into two genera, distinguished 

 by different external and internal characters, but especially by differences exhibited 

 by the genital organs. A more specialized diagnosis of the new genus will be given 

 in the låter part of this paper. Two species have been investigated : Metrocarpa leacJii 

 Savigny and Bolryllus schlosseri Pallas. As to the identification of the last- 

 mentioned species the reservation should be added that, from reasons mentioned 

 above, I' do not consider it as definitive, seeing that I had no type-specimens with 

 which to compare. The determination here made is based on the descriptions given 

 by Michaelsen and Van Name. 



As to the identification of the species leachi, I hope it will prove to be accurate, 

 inasmuch as I had the opportunity of comparing it with the type-specimen of 

 Botrylloides leachi Savigny in the British Museum. The individuals examined agree 

 as to external appearance, alimentary canal and reproductive organs; a rudimentary 

 brood-pouch has been observed even in the type. 



I should like in this place to put on record my sincere thanks to Mr. Randolph 

 Kirkpatrick of London for his kindness in placing the original at my disposal and 

 for the interest taken in procuring material for me with which to carry out the 

 co m parison. 



The structure of the reproductive apparatus is here represented by descriptions 

 of certain stages in the development of the individual. It develops early, persists 

 for a short time during the season of sexual maturity and then disappears. 



For the excellent drawings appearing in the text and on the plate I am in- 

 debted to the eminent artist Georg Liljevall. 



1 Herdman, W. A., »Challenger». Report 14. Ascidise composita?. Edinburgh 1886. 



2 Van Name, W. G., Ascidians of the West Indian Region and Southeastern United States. Bull. Americ. 

 Mus. Nat. Hist. Vol. 44. New York 1921. 



3 Michaelsen,W., Die Botrylliden und Didemniden der Nordsee in: Wiss. Meeresunters. d. deutschen 

 Meere in Kiel u. d. Biol. Anstalt auf Helgoland. N. F. Bd. 14. Oldenburg i. 0. 1921. 



