284 Transactions of the Society. 



Froinmenters Haltcria hlpartita ("Etude sur les Microzoaires," 

 Paris, 1874), but he seems to be too generous with the French 

 author's observations. Frommentel, in this latter work, describes 

 no less than nine new species of Haltcria (bipaiiita, vorax, miaima, 

 riridis, verrucosa, volrox, ovata, acuta, lohata), but in a few lines 

 only, and with such defective drawings that all these species are a 

 puzzle, and might l>e reduced to one or two. As, however, all 

 these species possess the wreath of leaping setai characteristic of 

 the genus Haltcria, none of them can be possibly united to 

 A7'achnidiu7n. 



After the publication of Kent's important work, nobody, to my 

 knowledge, met with an organism related to this group, though 

 Biitschli has a few words about it.* As for Delage (Zoologie 

 concrete), he simply indicates (in his " Index for Genera," p. 555) 

 the genus Arachnidium as synonymous with 3Iesodinium, and 

 nothing more. Thus Kent's observations seem to have been almost 

 i<^nored, and these " cilia which resemble rather small flexible 

 tentacula " appear not to have met with any serious consideration. 



And yet Kent is possibly quite right. At all events, I am 

 entitled to speak of an Infusorian whose locomotive organs are not 

 cilia nor setse, but flexible tentacula, and, if my observations 

 necessitate at least the creation of a special genus, this genus would 

 be very nearly related to Arccchnidium . 



The representative specimens of this ncM' genus, " Arach- 

 nidiopsis," were all found in the same station, Florissant near 

 Geneva, in the property of my friend, the botanist H. Komieux. 

 There can be seen a small pond, with gold-fish and aquatic plants, 

 especially exotic Nymphca and Nuphar, and it is vinder the water- 

 lilies that, as far back as 191B, I found the first Arachnidiopsis, a 

 single specimen, unluckily, which, though examined at length, 

 would not have allowed of any idea of publication ; but on 

 January 17 of this year (1918), a second specimen was found, and 

 lastly, a third one on the 1st of March. Since that time, and in 

 spite of frequent visits to this same locality, no further specimen 

 has been obtained ; but as the three specimens studied were observed 

 at length and showed an absolute concordance in all their details, 

 the facts are now sufficient to allow of a description of this very 

 curious type. 



Araclinidiopsis paradoxa — such is the name which I apply to it 

 — is a rather small Infusorian, 48 //. in length and about 40 [m in 

 breadth, egg-shaped, roundish or very little compressed (elliptical) 

 in its transverse section, but distinctly and broadly truncated at 



* Page 1732 of his work on Protozoa (Bronn's Thierreich) : " Zu Stromhidium 

 gehoren wahrscheiulichauch.4rac7midi«mgfZo6o??w«(Siisswasser)und4.coni>oZMiziw 

 (Meer) Kent's, welche beide auf Untersuchungen friiherer Zeit (1872 und 74) 

 basiren. Der unterscheidende cbarakter soil die tentakelformige lilUmg der 

 adoralen Cilien s'.ia, welche ich iiberhaupt bezweifle." 



