430 



SCIENCE 



[N. S. Vol. XLII. No. 1082 



of air by charcoal cooled to the temperature 

 of liquid air. 



The second method of showing the absorp- 

 tion of air, due to Dr. L. T. Jones, is at once 

 clear by an inspection of B in the figure. 

 The vertical stem, up to the branch leading to 

 the charcoal bulb, should be at least 78 cm. 

 long. This stem may also have an enlarge- 

 ment about half way up as shown. A valve 

 should be included to protect the charcoal 

 when not in use. Before starting the exper- 

 iment the valve is opened and the tube 

 mounted in a bath of mercury. Liquid air is 

 then applied to the charcoal bulb. The ab- 

 sorption proceeds slowly at iirst, but soon gains 

 headway as the charcoal cools. The speed that 

 the mercury column acquires as it rises up 

 through and fills the enlargement is surprising. 

 Even with the ratio of volume of tube to char- 

 coal as shown in the figure (approximately 

 4 :1) the mercury column will mount to nearly 

 full atmospheric pressure in the short space 

 of five or six minutes. 



Added interest is to perform the two ex- 

 periments simultaneously. 



Chas. T. Knipp 



Laboratoet op Physics, 

 xjniveesity of illinois, 

 August, 1915 



OCCURRENCE OF THE PROTOZOAN, COLAOIUM 

 MULTOCULATA KENT, IN IOWA 



In making collections of Daphnia, and other 

 Entomostraca, on October 31, 1914, the writer 

 discovered a small pond near Iowa City, Iowa, 

 which fairly teemed with Daphnia of a strik- 

 ing green color. 



Examination of these specimens in the labo- 

 ratory revealed the cause of the coloration to 

 be myriads of individuals of the Protozoa bear- 

 ing chromatophores and being attached to the 

 surface of the Daphnia completely covering, 

 not only the body proper, but even the appen- 

 dages in many cases. 



These Protozoa yielded themselves readily to 

 identification as belonging to the genus Cola- 

 cium — Flagellates closely related to Euglena 

 but differing therefrom in one essential, among 

 others, of having a sedentary attached stage as 



well as a free-swimming stage. In the seden- 

 tary stage the individual zooids are attached 

 by pedicles to some object or, as is more often 

 the ease, to some other form of animal life. 



Kent (1881) mentions, at the close of his 

 discussion of the Colacium, a supplementary 

 species for which he proposes the provisional 

 name of Colacium, multoculata. It is with his 

 description of this species that the animals 

 under the observation of the writer most favor- 

 ably compare. 



As with Kent the writer demonstrated a very 

 short pedicle and in no case was more than a 

 single individual found on one pedicle. There 

 is a general tendency for the animal to assume 

 a quadrate-elliptical form in outline both when 

 free-swimming and fixed, with an occasional 

 broadening near the distal end. The shape is 

 subject to more or less continual change. The 

 chromatophores are very large and seem to be 

 distributed near the periphery of the cell. 

 Kent describes the presence of from two to 

 four red spots instead of the single one com- 

 monly present and from this character pro- 

 poses the name of the species. By far the most 

 of the specimens examined by the writer pos- 

 sessed but one spot, some half dozen individ- 

 uals from the many showed from two to four 

 as described. In as much as the differing 

 specimens agreed in all other essential char- 

 acters they were undoubtedly variations of the 

 same species. The possession of a flageUum 

 by the free-swimming form was amply demon- 

 strated. 



Edmondson in his treatise on the Protozoa 

 of lowa'^ includes Colacium in his key to 

 genera but states that no species of this genus 

 has been reported within the state. It is prob- 

 able that other species closely related to the 

 one forming the subject of this note may be 

 added to the list of Iowa Protozoa. 



D. M. Brumfiel 



Laboeatoeies of Animal Biology, 

 State University of Iowa 



spore measurements 

 The usual way of giving measurements of 

 spores as width by length in /a is clear and 

 1 Davenport Academy of Seiences, 1906. 



