88 NATURAL SCIENCE [August 1898 



young ones, which, we learn with regret, are fed largely upon small 

 chickens. But, lest it be supposed that this kite should be banned 

 as vermin, we hasten to observe that its diet is very varied, 

 including worms, small crustaceans, dragon-flies, grasshoppers and 

 other insects, frogs, toads and water-newts, lizards, snakes of two 

 species, and five species of fish ; not to mention small mammals, 

 such as moles, shrews, mice, and (last, but not least) land- voles, 

 which are the bane of agriculturists. 



An Alga parasitic ox Ophiurids 



The occurrence of Algae in intimate connection with the bodies of 

 living animals is well known. Such are the yellow cells (Zooxan- 

 thella) of radiolarians, the green alga, ZoocMorella, found in many 

 infusorians, in Spongilla, Hydra, in various rhabdocoele turbellarian 

 worms, and so forth. But in all these cases the relation is one of 

 symbiosis, on the give and take principle. Lately, however, Dr Th. 

 Mortensen has described in Videnskabelige Mcdddelscr (1897, pp. 

 322-324) a species (probably a new one) of the green alga 

 Dactylococcus infesting the brittle-stars Oplvioylyplia texturata and 

 0. albida. It forms dark-green patches on both disc and arms, 

 on both upper and under side, sometimes in small excavations in 

 the calcareous plates. Its peculiarity is that it eats away the 

 skeletal substance and, apparently, does not pay for it. It is a 

 true parasite. 



Paper 



Since every scientific man should believe that his work is of per- 

 manent value, and should avoid publishing anything in which he 

 does not so believe, it becomes of some interest to him to see that 

 the paper upon which his articles are printed is of a quality 

 warranted to last. Therefore we recommend our readers to consider 

 with care the valuable report printed in the Journal of the Society 

 of Arts for May 20, in which a Committee appointed for the special 

 purpose, give the results of their investigation into numerous 

 printing papers. The disintegration of the fibre of papers is, as a 

 rule, referable to acidity in the case of rag papers : while, in 

 those made from wood-pulp it is due to oxidation, and is accom- 

 panied by an alkaline reaction. The discoloration of papers is pro- 

 portional to the amount of rosin which they contain. The Com- 

 mittee, therefore, advocates the following specification as that of a 

 reliable paper : — "Fibres : not less than 70 per cent, of fibres of the 

 cotton, flax, and hemp class. Sizing : not more than 2 per cent, 

 rosin, and finished with the normal acidity of pure alum. Loading : 

 not more than 10 per cent, total mineral matter (ash)." 



