I. ROBINSON — ON A MICROSCOPICAL AQUARIUM. 1 1 3 



Attached to a fragment of Riccia flnitans, I was so fortunate as 

 to tind representatives of five ^peeies of the collared monads. One 

 of these, the heautiful and delicate Monosiga glohosa, is in form 

 very similar to Monosiga gracilis, a representation of which, under 

 the extraordinary maguitication of 8000 diameters, forms the 

 frontispiece to Mr. Saville Kent's ' Manual of the Infusoria.' 

 Another, llonosiga Sfei)iii, which is of smaller size, has the singular 

 habit of attaching itself to the stalks of Vorticella (on one such 

 stalk I counted eighteen of these zooids, and they did not appear 

 to be at all discomposed by its frequent contractions and exten- 

 sions). Of two others, Salpingwca gracilis possesses a lorica or 

 sheath on a long pedicle, within which it resides ; and Salpingceca 

 fiisiformis has a most gracefully-formed lorica, but no pedicle. And 

 lastly there was a form individually similar to Monosiga glohosa, but 

 instead of appearing singly, grouped in clusters of from two to six 

 npon each pedicle, and resembling Codosiga grossularia, as described 

 by Mr. Kent. 



The transparent collar-like extension of these organisms is of so 

 extremely delicate a character that it is a matter of some difficulty 

 to succeed in clearly defining it. To do so requires good optical 

 appliances, and very careful illumination. Its shape may be de- 

 scribed as resembling that of a wine glass, and is said by Mr. Kent 

 to be " infundibuliform." In consequence of its perfect trans- 

 parency it is generally observable as a line on either side, while 

 the fiagellum may be seen waving about between. Its presence 

 throughout may, however, often be known by the small particles 

 of matter which adhere to it, and which may be seen to travel 

 slowly upward on its outer surface and downward within, in order 

 that they may be conveyed to the food-receiving portion of the 

 body, which is situated within the base of the collar. 



I have also found many specimens of Floscularia ornata, which, 

 with its long slender cilia, is a very interesting object for the micro- 

 scope. It is frequently found in this neighbourhood, and is usually 

 attached to one of the slender-leaved water-plants. It possesses a 

 case or sheath around its body, which, however, in consequence of 

 its perfect transparency, is not easily seen. When retracted, the 

 long cilia — which probably number several hundreds — project in 

 the form of a single pencil, but when fully expanded they radiate 

 in all directions from five lobes, and are of the most extreme 

 tenuity. It is a very pretty sight to watch their gradual expansion. 



Another interesting animalcule of somewhat larger size which I 

 have met with is the crown-animalcule, Stephanoceros Eiclihornii. 

 It possesses five long arms covered with cilia, which, when ex- 

 panded, form a sort of net for the capture of its food. It has also 

 a gelatinous sheath, which, although very transparent, is more 

 easily seen than that of Floscularia. 



A specimen of Chcetospira was easily recognizable by its pecu- 

 liarly twisted form when extended. From its position on the 

 weed to which it was attached, its lorica was not visible, and I am 

 therefore unable to say to which species it belonged. 



VOL. II. — PART III. 8 



