526 THE MICROSCOPE. 



developed. It increases both, by budding and by ova, 

 both of which conditions are shown in Plate IV. No. 98. 

 The ova are generally seen enclosed in the transparent 

 case of the parent. In Lophopus and most other fresh- 

 water genera, such as Gristatella, Plumatella, and A Icyo- 

 nella, the neural margin of the lophopore is extended into 

 two triangular arms, giving it the appearance of a deep 

 crescent. 



Alcyonella is a genus of fresh-water polyzoa, found 

 usually about the autumnal period of the year in the 

 several Docks at the East end of London, adhering to 

 floating pieces of timber. It assumes the form of an 

 irregular sponge-like mass, with an aggregation of mem- 

 branaceous tube-like openings covering the surface. 

 From these openings, the polypes are seen to project, the 

 mouths of which are encircled with a single series of 

 filiform ciliated tentacles, which keep the surrounding 

 water in active motion. The polypidom seen in water 

 has the appearance of a blackish-green sponge. 



Trembley gave an interesting account of the family of 

 Alcyonella; and Mr. J. Newton Tomkins favours us with 

 the following observations on the development of the 

 Alcyonella stagnorum (fluviatella) : — 



"The ova now under examination (|-inch obj. a. eye- 

 piece — 100 lin. diam., Wollaston's condenser), are the 

 products of some healthy specimens of Alcyonella stag- 

 norum given me by Mr. Lloyd, and sketched in full 

 activity in September 1856. Soon after this period 

 their movements decreased in energy, numerous ova were 

 detached, which floated to the surface of the water of 

 the jar in which they were confined, and in the course 

 of a very few weeks no trace remained of the parent 

 animals, except a spongy mass of an almost gelatinous 

 character, which still exists, though devoid of definite 

 form, and appears composed of a mass of broken and 

 disorganized cells. 



" In November, with a view of preserving the water in 

 a normal condition, I introduced a sprig of Anacharis 



a rich nervous plexus resting on the trunk, and connecting the ganglia just 

 mentioned, as well as the b isal ganglia of the individual polypides." For 

 further account, see paper in the Micros. Joum. vol. i. New Series, p. 330. 



