82 Mr. Thompson on an Alga which colours Bally drain Lake. 



I witnessed in various instances; but under such circumstances 

 only did I ever perceive any motion in this alga*. 



In some respects the Anab. spiralis resembles the Anab. 

 impalpabilis, Bory, as described in the ^ Encyclopedic Metho- 

 dique/ but its dull green unlustrous hue on paper is quite op- 

 posed to that of the species just named, which is described — 

 " Preparee sur le papier, oii on a facilite son developpement, 

 elle est de la teinte la plus brillante, tirant sur celle de Foxide 

 de cuivre, et luisante comme si on I'eut enduite d'eau de 

 gomme." Besides, were this species of the exact spiral form 

 of that under consideration, this character would not I con- 

 ceive have been unnoticed in the description. 



Anabaina flos-aqu(£^ Bory. Byssus flos-aqucB, L. This spe- 

 cies may here be noticed, after having passed the judgement 

 of my friend W. H. Harvey, Esq. It attracted my attention 

 when tinging with its delicate green hue the margin of the 

 smallest ? of the lochs Maben in Dumfries-shire, or that near- 

 est to Jardine Hall (on the road from the village of Loch- 

 maben), as I drove thither on the 15th Aug. 1838 ; the day 

 was calm and bright. My specimens tinge the paper with a 

 verdigris colour, and are quite dull or wanting in any lustrous 

 appearance. This species is introduced here on account of 

 its having been erased of late years from the British Flora. 

 Hudson and Lightfoot included it, but without assigning to 

 it any British station or locality. 



Aphanizomenon recurvum, Morren. On the 25th July 1838, 

 I observ^ed on the surface of sheltered creeks in Ballydrain 

 Lake a very minute Alga having the appearance of powdered 

 verdigris. On examining it after I had reached home, I could 

 merely, as in the instance of the Anabaina procured on the 



* Bory St. Vincent remarks of the genus Anahaina — " Leur mouvement 

 offreun espece de rapport avec ceux au moyen desquels ambulent les lom- 

 brics; ils sont progressifs, et les courbures qu'ils determinent sont dune ex- 

 treme lenteur. C'est a I'aide de cette faculte ambulatoire que I'on voit sur- 

 tout les especes aquatiques s'elever a la surface de I'eau, le long des Con- 

 ferves et des debris des vegetaux, ramper a la surface des roseaux et des 

 carex, penetrer la vase et les Oscillaires, en les surmontant, ce que leur a 

 merite le nom tire du grec, pay lequel nous avons propose de les designer." 

 — Ency. Method. This author ranked the AnabaincB in the animal king- 

 dom. 



