GLOSSARY. 69 



Interoper'culum (L. inter, between; operculiim, a lid). A 

 bone which in the Teleostean fishes lies beneath the 

 suboperculum, and is connected with the hyoidean arch, 

 and also with the angular piece of the lower jaw. 



Interos'seous (L. inter, between; os, a bone). One of a pair 

 of muscles on the ventral aspect of the fifth digit of the 

 manus. 



Interpedun'cnlar space. The lozenge-shaped area on the base 

 of the cerebrum which is limited in front by the optic 

 tracts, and-behind by the peduncles or crura cerebri. 



Interspi'nous (L. inter, between). Between the spines. Ap- 

 plied specially to certain bones which, in the dorsal fin of 

 Teleostean fishes, are developed between the spines of the 

 vertebrae. 



Intertransversales (L. inter, between ; transversus, transverse, 

 oblique). Short muscles passing from vertebra to vertebra, 

 between the transverse processes. 



Interver'tebral (L. inter, between). Between the vertebrae, as 

 the intervertebral cartilages. 



Intes'tine (L. intestlnum, a gut). That portion of the ali- 

 mentary canal which lies between the stomach and the 

 anus. 



In'tine (L. in, within). The inner coating of a pollen grain. 



Intralo'bular (L. intra, within). Within a lobule; specially 

 applied to the minute veinlet occupying the centre of 

 each lobule of the liver. 



Intrape'talous (L. intra, within ; Gr. petalon, a leaf). Applied 

 to those bands of spines which, in the Echinidea, encircle 

 the inner terminations of the ambulacra. 



Inva'gination (L. in, into; vagina, a sheath). The pushing of 

 one part of a hollow structure into another part, as may 

 be done with the finger of a glove. 



Inver'tebrata (L. in, not ; vertebra, a joint of the backbone). 

 Those animals which are destitute of a skull and vertebral 

 column. 



Involu'crum (L. a wrapper). A sheath which surrounds the 

 base of the thread cells in the Siphonophora. 



Involution (L. in, in ; volvo, I roll). Rolling in. Backward 

 growth, such as the return of the uterus to its normal 

 condition after parturition. 



I'ris (L. a rainbow). The contractile curtain which is per- 

 forated by the pupil, and which forms the coloured portion 

 of the eye. 



