322 Mr. Poulton's//tr^/icr notes upon the 



interior surface of the apex. The retractor muscle of 

 the snail's tentacle is well known to have this arrange- 

 ment, and I have found striated muscle fibres similarly 

 attached to the eversible glands of hymenopterous larvaB. 

 The most striking of all the instances of this kind of 

 protrusion is, I think, afforded by the well-known flagella 

 of the larva of D. vinula. The pink flagella are very 

 long and narrow, and are protruded with great rapidity. 

 At the base of each flagellum there is a small transparent 

 area extending round the whole circumference, and 

 through this, as through fi window, the processes of 

 invagination and evagination can be readily watched. 

 When the invaginating flagellum has shortened to half 

 its length, the tip has, of course, been drawn inwards as 

 far as the transparent base, and a pink line is seen in 

 the axis of the latter, rapidly lengthening inwards until 

 the whole axis is pink. As invagination becomes com- 

 plete the pink axis disappears inwards as the transparent 

 part is itself invaginated. The same phenomena are 

 also seen in evagination in the reverse order. The 

 protrusion and withdrawal of claspers seems to be 

 essentially due to the same process. The whole shape 

 of the larva also depends on the fact that it contains 

 fluid under considerable pressure, as can be readily seen 

 in a dying larva, in which the muscles have lost their 

 tone. Under these circumstances the larva entirely 

 collapses, and the only traces of movement are seen in 

 its thoracic legs, which depend upon their own muscles, 

 and are not moved by the fluid (although the elevations 

 upon which they are placed owe their firmness to this 

 cause). 



It is hardly necessary to point out that this con- 

 struction is extremely dangerous, for a very slight 

 wound entails great loss of blood, while a moderate 

 injury must prove fatal. The larvae of S. ocellatns (and 

 many others) nibble off each other's horns, and the 

 wounded larvae 'although they do not seem to be aware 

 of the injury) lose a great deal of blood, and, although 

 they may recover, are generally stunted ; and often, I 

 am sure, the loss of blood proves fatal. If the wound 

 be at all extensive the fat-body and viscera protrude, 

 owing to the pressure on the side distal to the wound 

 (that on the proximal side having been relieved by 

 escape of blood). It is, I believe, in consequence of 

 these facts that the various means of protection in larvae 



