69 



proximal one. Ovisacs generally narrow oblong or fusiform in shape and, as a 

 rule, diverging greatly, in some cases, however, more appressed to the body. 

 Seminal receptacle with the posterior part very little produced and slightly emarg- 

 inated in the middle. Spermatophores attached to the genital orifice lageniform 

 and closely juxtaposed. 



Body of a clear yellowish grey colour, with a more or less distinct 

 olivaceous tinge, and variegated with dark transverse bands at the end of some 

 of the segments, as also across the cephalic part; anterior antennae generally 

 with 2 very conspicuous dark bands, the one occupying the 2nd and 3rd joints, 

 the other the 10th and llth joints. 



Length of adult female about 1.80 mm. 



Remarks. This form has generally been recorded by recent authors under 

 the name of Cyclops albidus Jurine, a name which is very little significant, as 

 the present species in most cases exhibits a rather conspicuous colouring of the 

 body. For the reason noted above the name ought also to be rejected, and to 

 be replaced by that proposed by Koch, which has the precedence to the name 

 tenuicornis given to the species by Glaus. The Cyclops gyrinus of Forbes is 

 unquestionably this species, and is not, as opined by Dr. Schmeil, identical with 

 C. distinctus Richard. 



The present species is nearly allied to the 2 preceding ones, but is of 

 smaller size, and moreover easily recognisable from them by the shortness of 

 the outermost caudal seta. The manner in which the ovisacs are born is also 

 very characteristic, though in some cases specimens are found in which they are 

 more appressed to the body, a circumstance which at first led me to the erro- 

 neous opinion that these specimens might belong to a different species. 



Occurrence. This is one of our commonest Cyclopids, being found both 

 in small ponds and ditches and in large lakes. In the latter it not only occurs 

 at the borders, but descends to rather considerable depths. In the lake Mj0sen 

 I have even taken it in great numbers down to 50 fathoms together with 

 Cyclops vulgaris. 



Distribution. Throughout Europe, northern part of Asia, Central Africa, 

 Australia, North and South America, Hawaii Islands. The distribution of this 

 form is accordingly almost cosmopolitan. 



