Mr. Darwin on several Planarise. 241 



A specimen witli different fruit was found by my daughter on 

 tlie shore at Ardi-ossan. It had not the hemispherical urceolate 

 capsules, but it had instead purple tufts not unlike the fruit of 

 Odonthalia dentata : they had the appearance of a little mass of 

 short truncate ramuli. In general they were sessile, but in one 

 case the mass was raised on a short purple pedicel (PI. IV. 

 %. 3.«). 



The third kind of fructification consists of granules imbedded in 

 the branches. In the specimens with tufted fructification these 

 were small, of a purple colour, and situated in the upper ramuli, 

 to which they gave a dotted appearance (PI. IV. fig. 4. b). What 

 I am disposed to think the most common kind of fructification 

 occm-red in other specimens, viz. large bi/ff-coloured granules 

 generally imbedded in distorted ramuli (PI. IV. fig. 5). At 

 times they are only partially imbedded, producing jjrotuberances 

 which are filled with countless very minute granules around the 

 large granule. At other thues the large buff"-coloured granules 

 are quite external but sessile, at a certain stage falling off, not 

 to be lost in the depths of ocean, but in all likelihood to produce 

 a fresh generation of young Gluiosiphonia. 



Of these large bufi" granules there are seldom more than three 

 in one branch, whilst the small granules imbedded in the ulti- 

 mate branches are like purple points or dots, very numerous, but 

 quite distinct from each other. 



I may also state that the ultimate ramuli generally seemed 

 jointed like Ceramium ruhrum, and of a pink colour ; yet there 

 were occasionally intermingled little branches with fawn-coloured 

 joints and white articulations so very like Ceramium diajihanum, 

 that I should have concluded that this Ceramium had fastened as 

 a parasite on the Gloiosiphonia, had I not seen that the same 

 little branch which set out as a Gloiosiphonia, without any warn- 

 ing given suddenly assumed the aspect of C. diaphanum. 



EXPLANATION OF PLATE IV. 

 Fig. 1. Capsule o^ Polysiphonia parasitica. 



Fig. 2. Polysiphonia parasitica, with granules and dwarf capsule. 

 Fig. 3. Gloiosiphonia capillaris : a, tut't of fruit. 



Fig. 4. Ditto, ditto : a, capsule ; b, small imbedded granules. 



Fig. 5. Ditto, ditto, with large granules in distorted ramuli. 



XXIX. — B7'ief Descriptions of several Terrestrial Planariee, and 



of some remarkable Maiine Sjjecies, with an Account of their 



Habits. By Charles Darwin, F.R.S., V.P. Geol. Soc. 



[With a Plate.] 



In my Journal I have given a brief account of the discovery of 



several species of terrestrial Planarice : it is my intention here to 



