276 



HARDWICKE'S SCIENCE-GO S S IP. 



[Dec. 1, 186S. 



their reception, just as the claws of the lion are re- 

 tracted during progression, the same muscles and 

 mechanical principles being called into play to fulfil 

 the purposes of this almost invisible parasite as are 

 applied to enable the terrible king of beasts to ac- 

 complish the ends for which he was created. 



Fig. 254. Slug Parasite, x ISO. 



Eig. 256 shows the foot when the claws are thus 

 thrown back in reserve, ready in a moment to come 

 down, one on either side of the pad, and insure a firm 

 hold on the slimy epithelium of Limax. 



Fig. 255, x 450. 



Fig. 256, X 450. 



He has no eyes : " the parasitic mites arc entirely 

 deficient in these organs," says Siebold, "but are 

 provided with a very debcatc sense of touch both in 

 the palpi and in thejfeet." The same distinguished 

 naturalist— coinciding with Latreille— states that 



the whole class Arachnoidal have no true mandibles, 

 the organs commonly so called being "antenna? 

 metamorphosed into prehensile and masticatory 

 parts, since the nerves of those organs do not arise 

 from the abdominal ganglia, but directly from the 

 brain, as those of the antennae of Crustacea and 

 Insecta." 



After a great expenditure of patience, and much 

 manoeuvring with light, we at last succeed in 

 getting a satisfactory "definition" of the oesophagus, 

 the five digestive cceca, and the intestine terminating 

 in the under side of the abdomen : placed in the 

 focus of concentrated rays collected from a Bockett 

 lamp by a parabolic illuminator, the swift atom 

 shines out from the darkness like glittering crystal, 

 while the piercing light, aiding "penetration," 

 enables the magic glasses to bring out the trachese 

 and air-saks, and to fathom the recesses of bags 

 and tubes. "We cannot make out the heart and 

 blood-vessels ; the world-famed German above 

 quoted pronounces that both are absent, — " There is 

 therefore no regular circulation, but the nutritive 

 fluid fills 'all the interstices of the body, and, by aid 

 of the muscular movements and the contractions of 

 the intestinal canal, is transferred in an irregular 

 manner hither and thither in the visceral cavity and 

 in the extremities." It may seem presumptuous to 

 question this very decided dictum, yet I am bold to 

 hazard the remark that, in my very humble opinion 

 the entire absence of both heart and blood-vessels in 

 a creature of such high and complex organization is 

 opposed to all analogy, and I venture tc express my 

 belief^that in due course of time, with the ever im- 

 proving instruments and means of examination, 

 some invincible pursuer of Nature's unrevealed 

 secrets will discover and delineate for us either a 

 heart or an articulated dorsal-vessel even in the tiny 

 Philodromus Limacum. 



Bury Cross, Gosport. J. Y. H. 



SCALAPJFORM TISSUE. 



rpHE arrangement of the scalariform tissue in the 

 •*- rachis of ferns presents us with several points 

 of interest. In the first place, the scalariform tissue 

 itself seems to be formed by a spiral thickening of 

 the walls of the vessels, leaving regular elongated 

 spaces not so thickly covered with the secondary 

 deposit ; for the vessels occasionally break up into 

 spiral ribbons (fig. 257 p.) Then, not only each 

 genus, but each species, seems to have its own 

 peculiar arrangement of tissue ; 

 possible from a mere section 

 determine the genus, and even 

 fern. 



The accompanying figures represent slightly mag- 

 nified sections of fourteen of the more common 

 ferns. 



so that it seems 

 of the stem to 

 the species of a 



It will be seen at a glance how different the 



