1886.] 



MICROSCOPICAL JOURNAL. 



229 



The change of shape in the present 

 species consists chiefly in the assump- 

 tion of a subspherical contour, after 

 prolonged confinement beneath the 

 cover-glass. At other times the al- 

 teration is very slight. 



In all the Choano-Flagellata, so far 

 as I am aware, excrementitious frag- 

 ments are extruded, and food-particles 

 are engulfed at some point within the 

 area surrounded by the base of the col- 

 lar, the collar itself presenting two dis- 

 tinct currents of its substance, an ex- 

 ternal upward and an internal down- 

 ward one, the latter conveyingthe food- 

 particles directly to the ingestive re- 

 gion. With the present species of 

 Desmarella^ however, while the ex- 

 crementitious matters are expelled 

 from the space within the base of the 

 collar, the food is engulfed at a point 

 near the basal attachment of that ap- 

 pendage but external to it, a wave of 

 the body sarcode advancing to receive 

 and surround the adherent morsel. 

 The external current of the collar-like 

 film is here the reverse of that which 

 obtains in the species of the other 

 genera of this order, as is evidenced 

 by the movement which slowly car- 

 ries the adherent particle downward 

 toward the body, but that the internal 

 flow is upward, as is probable and 

 almost a necessity under the circum- 

 stances, I have not been able to posi- 

 tively see, since the floating materials 

 so soon come within the influence of 

 the whirling flagellum. This pecu- 

 liarity in food habit is an important 

 and interesting characteristic of this 

 species at least ; it is probably an un- 

 observed custom in all the members 

 of the genus. 



The colonies were abundant in the 

 water collected from a shallow pond in 

 the early part of December, 1S85, and 

 left standing in a warm room. Their 

 movements are rotary, and compara- 

 tively slow. 



The species dift'ers from Desnia- 

 rella phalanx (Stein) S. K., the 

 hitherto only known fresh-water 

 form, in the general aspect of the 

 colony, that of the former resem- 



bling D. moniliformis^ S. K., in 

 being composed of zooids laterally 

 united in long chains. A cluster of 

 the species here described is repre- 

 sented by the diagram shown in 

 fig. 3, each little ring there rep- 

 resenting' one zooid. 



Imbedding in Celloidine. 



For the benefit of those of our read- 

 ers who have not seen accounts of the 

 method employed in the use of celloi- 

 dine for section-cutting we copy the 

 following accounts from (V) Sedgwick 

 & Wilson's Biology* and from (II) 

 Prof. C. S. Minot's Notes on His- 

 tological Technique, t 



I. The celloidine method is espec- 

 ially applicable to delicate vegetal 

 tissues. After dehydrating the object 

 thoroughly in alcohol, soak it 34 hours 

 in a mixture of equal parts of alcohol 

 and ether. Make a thick solution of 

 celloidine in the same mixture and 

 soak the object for some hours in it. 

 It may then be imbedded as fol- 

 lows: — Dip the smaller end of a 

 tapering cork in the celloidine so- 

 lution, allow it to dry for a mo- 

 ment (blowing on it if necessary), 

 and then build upon it a mass of 

 celloidine, allowing it to dry for a 

 moment after each addition. Trans- 

 fer the object to the cork and cover it 

 thoroughly with the celloidine. Then 

 float the cork in S2-85 per cent, alco- 

 hol until the mass has a firm consist- 

 ency (24 h.). It must then be cut in 

 the microtome with the oblique knife, 

 which must be kept dripping with 

 S2-85 per cent, alcohol. Keep the 

 sections in 82-85 per cent, alcohol 

 until ready to mount them ; then soak 

 them for a minute in strong alcohol, 

 transfer to a slide, pour on chloroform 

 until the alcohol is removed, drain off' 

 the liquid, quickly add a drop of bal- 

 sam, and cover. 



II. Prof. Minot, in his 'Notes,' 

 says : — 



* Page 189. 



t Zeitsche f. w. Mikros., vol. iii, p. 174. 



