Nov. 5, 1874] 



NATURE 



The quadrate is a stout bone, having three well-defined 

 processes, one forming the articular surface for the man- 

 dible ; a second, answering to the otic process of the 

 primitive suspensorium, articulates with the squamosal ; 

 and the third, or orbital process, projecting forwards and 

 upwards, is the pedicle or true apex of the mandibular 

 arch. The otic process, besides articulating with the 

 squamosal, bears a small facet for the prootic ; this, in 

 many birds, is developed into a distinct secondary head. 



Immediately behind the quadrate is seen the large 

 tympanic cavity ; this is banded above Ijy the supra-occi- 

 pital and squamoid, below by the bisi-temporal, behind 

 by the ex-occipital, and in front by the basi-sphenoid ; it 

 sends into the latter a diverticulum, the anterior tympanic 

 recess, and a second or posterior recess into the supra- 

 occipital, through the diploe of which it is continuous, as 

 in the crocodile, with the tympanum of the opposite side. 

 The fowl resembles the ostrich, and differs from most 

 other birds in being wholly devoid of a tympanic bone. 



The lower jaw consists of the s.ame elements as already 

 described in the snake, except that the coronary is absent 

 in the fowl, though present in most birds ; in this stage 

 the five bones (articular, angular, supra-angular, dentary, 

 and splenial) are perfectly distinct, and Meckel's cartilage 

 yet remains of considerable size. 



The upper part of the hyoid arch is separated, as in the 

 snake and frog, to form with the stapes a columella am is. 

 From the oval, irregular, plug-like stapes proceeds a 

 slender rod of bone terminated by a triradiate cartilage, 

 of which the slender antero-infcrior bar is the infra- 

 stapedial, the broad somewhat expanded central segment 

 the e.xtra-stapcdial, and the postero-superior bar the 

 supra-stapedial. The latter is connected by an oblique 

 bar with the extra-stapedial. The stylo-hyal is repre- 

 sented by the free end of the infra-stapedial. 



The tongue-bone consists of a body made up of glosso- 

 hyal (formed by the union of the lesser cornua), basi-hyal, 

 and basi-branchial (uro-hyal) arranged in a linear series ; 

 and of two pairs of cornua, the anterior or cerato-hyals, 

 very small, and forming more lateral projections to the 

 body, and the posterior or epi- and cerato-branchials 

 (thyro-hyals), long and elastic, and embracing the occi- 

 pital. 



The development of the fowl's skull has been worked 

 out as far back as the fourth day ; but even at that early 

 period, when chondrification is only just beginning to set 

 in, it is impossible to demonstrate with certainty the 

 distinctness of many regions which are perfectly separate 

 at corresponding stages in the lower types. At the period 

 mentioned, the indifferent tissue of which the trabecular 

 are formed is perfectly continuous with that of the invest- 

 ing mass, and this again with that of the auditory c.ip- 

 sules. When, however, the process of conversion into 

 cartilage is complete, the apices of the trabecula; become 

 perfectly distinct from the investing mass, and form a 

 pair of backward-turned horns (often called the liiigiihc 

 spltcnoidalcs) on either side of the pituitary space. The 

 ear capsules, on the contrary, remain as undistinguishable 

 from the para-chordal region after chondrification as 

 before, and only acquire distinctness by ossification. 

 This rapid process ot fusion which takes place equally 

 between the masses of indifferent tissue constituting 

 the primordial skull, in the subsequently formed tracts 

 of cartilage, and in the various ossifications of a still later 

 period, renders the study of the bird's skull one of the 

 most difficult problems of craniology. 



The manner in which the hyoid arch is developed has 

 been worked out more exactly in the house-martin than in 

 the chick, in which, however, the process is essentially 

 similar. At a very early period the upper end of the arch 

 grafts itself on to the auditory capsule, and at the same 

 time becomes split up into three portions. The proximal 

 of these constitutes the columella, a plug of the auditory 

 capsule being before long cut out around its attached end 



to form the stapes. The middle is the stylo-hyal ; it is at 

 first connected to the columella by a tract of tissue but 

 afterwards fuses with the infra-stapedial element of the 

 latter. The distalpartion never becomes chondrified in its 

 upper portion, resembling in this respect the correspond- 

 ing structure in man (the stylo-hyoid ligament), but Ijelo'v 

 forms the lesser cornu of the hyoid bone, or cerato-hyal. 



The mode of formation of the complex basi-sphcnoidal 

 region is, perhaps, the most important point which yet 

 remains for consideration. No endogenous ossification 

 takes place in the cartilage of this part of the basis 

 cranii, but a pair of symmetrical ossific centres make 

 their appearance in the thick web of perichondrium 

 which underlies it, a third (median) centre appearing at 

 the same time in front of the other two in the fibrous 

 tissue below the ethmoidal cartilage. These ossifications 

 together represent the dagger-shaped parasphenoid of the 

 frog; the anterior is commonly known as the bisi- 

 sphenoidal rostrum ; the posterior pair, coalescing, form 

 the basi-temporal. Before they unite, however, ossification 

 extends from them into the overlying cartilage, and thus 

 the true basi-sphenoid is formed in a manner perfectly 

 unique among vertebrata. 



THE NEW VINE-DISEASE IN THE SOUTH- 

 EAST OF FRANCE * 



TLJ AVING thus far studied the spread of the new vine- 

 ^ '- disease and the extent of the ravages committed by 

 the Phylloxera, it is time to turn our attention to the 

 insect itself, and to state the results of scientific obsen-a- 

 tion of the manner in which it attacks the vine rootlets, 

 and the various circumstances and conditions which either 

 favour or retard the development of the disease. 



The Phylloxera is a very minute insect, measuring, 

 when fully grown, not more than l-33rd of an inch in 

 length. Its most striking feature is its proboscis, which 

 lies in a sort of groove on the under-side of the insect 

 and with which it pierces the roots on which it feeds. 

 This proboscis is very slender, and appears to be formed 

 of three tongues, a greater one in the middle, and two 

 more slender and shorter, on the two sides of it ■ it 

 resembles a brown thread bending round and insertino- 

 itself in the tissue. The base of the proboscis is a sort of 



The Phylloxera. 



flat and sharp-pointed blade, composed of brown parts 

 which prolong themselves into the tongues. The animal 

 raises this blade a little in applying its proboscis to its 

 food. The length of the sucker is equal to about half that 

 of the body of the Phylloxera, which doss not bury more 

 than half of it in the bark of the roots. By this sucker 

 the insect fixes itself to the spot which it has chosen, so 

 that it can be made to turn upon it as on a pivot. In 

 colour the Phylloxera, during the summer at least, is 

 yellow, but in the late autumn it turns to a copper-brown 

 tint, which lasts through the winter. The active life of 

 the Phylloxera lasts from the beginning of April till the 

 latter half of October. The insect hibernates through 

 the other months, though previous to the commencement 

 of hibernation the females who have laid eggs during the 



* Continued from vol. -v. p. 506 



