ON THE REPRODUCTIVE ORGANS OF HOLOZOA CYLINDRICA LESSON iii 



organs attain their full development early in the Antarctic summer, and the female organs later during 

 the full Antarctic summer. The former are thus mature in advance of the female. The conclusion 

 which might be drawn from these facts seems thus to point to the occurrence of protandry in 

 H. cylindrica. 



According to Hartmeyer and Michaelsen, and also Van Name (1945) other Polycitorid genera too, 

 for instance Sycozoa and Sigillina, are gonochoristic, the colonies and the zooids from the same colony 

 being either male or female (see Bronn's Tier-Reich). The fact that Holozoa cylindrica is herma- 

 phrodite raises the question whether these genera in fact also possess this peculiar character. 



In his paper Ascidiae Krikobranchiae von Neuseeland, den Chatham- und den Auckland-Inseln (1924), 

 Michaelsen has in some degree receded from this opinion. In the above-mentioned paper of his 

 he proposes to unite the nearly allied forms Holozoa and certain species of Sycozoa under a common 

 generic name Distaplia. — Holozoa and Distaplia are considered by Hartmeyer as identical (loc. cit. 

 p_ 1437). — In his diagnosis of the genus Distaplia Michaelsen mentions as one of the generic cha- 

 racters 'Personen zwittrig oder Kolonien getrennt geschlechtlich ; ein enggestielter Brutsack vor- 

 handen, i Embryo oder deren mehrere enthaltend' (loc. cit. p. 297). 'In der Gattung Distaplia s.s. 

 kommen dagegen sowohl Arten mit getrenntgeschlechtlichen Kolonien vor, sowie solche mit Kolonien, 

 deren Personen zwittrig sind' (loc. cit. p. 321). According to this author the species of this genus are 

 thus either gonochoristic or hermaphrodite. In Distaplia {Holozoa) cylindrica and the ' cerebriforme- 

 Gruppe ', the colonies and the zooids are of the same sex, but in other species of Distaplia they are 

 hermaphrodite. 



Taking into consideration what has been adduced above, it is evident that until further evidence is 

 forthcoming by way of thorough investigations nothing can be stated for certain, whether certain 

 Polycitorid forms are in reality gonochoristic, or whether, just as in Holozoa, an investigation of suit- 

 able material collected in various seasons might prove them to be hermaphrodite. 



LITERATURE 



Calman, W. T., 1895. On Julinia; a new geniis of Compound Ascidians from the Antarctic Ocean. Quart. Journ. Micr. Sci., 

 new sen, xxxvn. London. 



Hartmeyer, R., 1909-11. Ascidien in Bronn's Klassen und Ordnungen des Tier-Reichs. in, Suppl. Leipzig. 



191 1. Die Ascidien der Deutschen Siidpolar-Expedition i()oi-i<)02. D. Sudp.-Exp. xn. Berlin. 



Michaelsen, W., 1896-1907. Tunicaten, in Ergebnisse d. Hamburger Magalhaensischen Sammelreise 1892-1893, i. Ham- 

 burg. 



. 1924. Ascidiae Krikobranchiae von Neuseeland, den Chatham- und den Auckland-Inseln. Vidensk. Meddel. fra Dansk 



Naturh. Foren. Lxxvn. Odense. 



Van Name, W. G., 1945. The North and South American Ascidians. Bull. American Mus. Nat. Hist. Lxxxiv. New York. 



