444 LIFE : OUTLINES OF GENERAL BIOLOGY 



in to poisoning without making a struggle! Indeed, it may react so 

 effectively, by producing counteractives or anti-toxins, that the 

 animal becomes immune. 



In his recently published Gifttiere (1927), Prof. E. N. Pawlowsky 

 of Leningrad has given an interesting grouping. First of all, there 

 may be separated off those animals that have no special poisonous 

 organs or glands, yet may prove their virulence if they are used as 

 fo(xl, or if their blood, extracts, or exudations are introduced 

 experimentally or non-aggressively into some other creature. This 

 is a passive poisonousness, depending on some peculiarity in the 

 chemical composition of the poisoner's tissues. It is well illustrated 

 by most of the inflatable "Puffers" or "Globe-fishes", by the 

 "Blister-beetles", whose blood is rich in the poison cantharidin, 

 and by a number of parasites, such as threadworms, whose exudations 

 have a poisoning eftect. 



All the other poisonous animals, extraordinarily diverse in nature, 

 have this in common, that they have specialised structures or organs 

 for the preparation of the poison and its aggressive expulsion into 

 or on to a victim. Thus, to begin near the base of the genealogical 

 tree, there are the jelly-fishes and sea-anemones and Portuguese 

 Men-of-\\'ar, whose epidermis contains myriads of stinging-cells. 

 The ejection of microscopic las.soes liberates poisons, such as thalassin 

 and congest in, which are often very virulent, as bathers sometimes 

 discover. Besides discouraging the attacks of hostile animals, the 

 stinging threads often serve to paralyse and capture the small 

 organisms that are used as food. 



Another group may be defined to include a large number of 

 insects that exude irritant blood aggressively from various strategic 

 points on their body. The expulsion is sometimes a gentle exudation, 

 as in oil-beetles; but it may be energetic enough to deserve the name 

 of squirting, as in the large caterpillar-like larvieof the birch saw-fly. 

 There is an Algerian Locustid that squirts out a double jet of 

 orange-coloured blood to a distance of two inches! This is very 

 striking, yet it is also puzzling. For one cannot help thinking that 

 blood is much too precious to be utilised in this reckless way. 

 Perhaps the expulsion relieves blood-pressure; perhaps it does not 

 happen very often. 



The most highly evolved animal-poisoners are those that possess, 

 not only poison glands, but some specialised arrangement for 

 introducing the venom into a victim. Perhaps it might be useful to 

 condone and even adopt the peculiar use of the word "sting" to 

 denote any of these poisoning instruments, which are so diverse in 

 nature. The spider "stings" with its first pair of mouth-appendages, 

 the scorpion with a sharp spine at the end of its tail ; the duckmole 

 stings with a spur, the weaver-fish with a fin-ray; the procession 

 caterpillars and many others sting with their nettle-like hairs. How 



