size) are so good as to remove all doubt concerning their identity, even in the absence ol the 

 original plants which have unfortunately disappeared. The author discusses the propriety of 

 including the genus Corallina in the animal kingdom, and decides that the presence of the 

 "calcareous covering" precludes the possibility of regarding them as plants. They may indeed, 

 he thinks. form a connecting link between the two kingdoms. 



In iSi 2 Lamouroux ("Sur la classification des Polypiers coralligères non entièrement 

 pierreux" in Soc. Philom. N. Buil. Paris III. 1812. p. 186) divides off the six species known 

 as Corallina tridens, opuntia^ monik\ incrassata, Titua and discoidea from the genus Corallina 

 and unites them under the generic name of Halimeda, of which he gives a short diagnosis. 

 In 1816 the same author published his "Histoire des Polypiers Coralligènes fiexibles" wherein 

 he deals with the genus at some length and gives specific diagnoses and references to literature. 

 Even this author, however, wil! have none of this genus in the vegetable kingdom and is 

 inclined to be scornful about "a celebrated zoologist M. A. B", who declares H. Tuna to be a plant. 



The hrst definite record of the inclusion of H. Tuna in the vegetable kingdom, under 

 the name of Hormisus opuntioides vvould seem to have been in an unpublished MS. of Targioni- 

 Tozzetti entitled "Catalogus vegetabilium marinorum". Bertoloni mentions this MS. in his 

 Amoenit. Ital. 181 9. p. 281 ancl gives Hormisus opuntioides as a synonym of his name Fucus 

 Ser lolara (Bertoloni l.c. pp. 224, 316), thus following Targioni-Tozzetti's example in regarding 

 Halimeda Tuna as a plant. He says : "Cortice calcareo adventitio huc illue obtegitur : sed cortex 

 iste nullimodo ei proprius, nullumciue in recenti pulpae animalis vestigium. Textura vegetabilis". 



From this time onwards Halimeda was generall)- recognised as an alga and new species 

 were created from time to time by various authors. Dr. Harvey's views on the species limits 

 of Halimeda were broader than those of later writers and, as is shewn below in the systematic 

 treatment, his breadth of view is more than confirmed by the present investigation. 



Similar views as to species limits were not held by the late Prof. J. G. Agardh, who 

 treats of the genus in Till Algernes Systematik VIII. p. 77 — 89. This author is however the first to 

 suggest a fusion between the filaments of the central strand. He says: "Fila proprie axilia sunt 

 semper numerosa et longitudinaliter excurrentia, invicem conspicue distantia et intertexta et 

 sparsim forsan anastomosibus" . . . He then refers to the somewhat scanty knowledge of the 

 fructification which is described by Derbès et Solier ("Mémoire sur quelques points de la 

 Physiologie des Algues" in Comptes Rendus Suppl. T. I. 1856. p. 1 — 120. pi. 1 — 23); by 

 Bompard as a parasitic alga, under the name of Botryophora dichotoma, (Hedwigia n". 9, 1867. 

 p. 1 29) ; and by Zanardini, (Iconographia Phycol. Mediterr. Adriat. vol. III, tab. CXII. 1871. p. 129). 



In 18SS, Professor Askenasy published an account of the algae of the Gazelle (Forschungs- 

 reise S. M. S. "Gazelle". Th. IV. Bot. Alg. p. 1 1) and here for the first time is an attempt to classify 

 the species on other than external characters. This author gives a fuller description of the internal 

 structure of Halimeda than any previous writer and from an examination of the peripheral cells 1 ) 

 of the various species, pronounces these cells to be characteristic as regards form and size for 



1) I \vould here explain my use of the term "peripheral cell" in speaking of the termination of the filaments at the periphery 



of the joints. Wc In. 1 word to press the "Rindenschlauche" of the Germans, for "peripheral tubes'' does not quite meet 



e and might lead to misunderstanding. '1'lie word "cell", though technically inaccurate, seems to me to bc therefore preferable, 

 ially since these structures have the appearance. in surface view, of cellular tissue. 



