KANSAS Academy of science. 



"It is well known that the protozoans — sponges, crelenterates, infusoria, etc. — de- 

 pend for sensation and motion upon the irritability and contractability of pro- 

 toplasm," says Mr. A. S. Packard ( " Standard Natural History " ). Again: "A genuine 

 nervous organization for the first time appears in the jelly fishes. The echinoderms, 

 starfish, etc., have a mere nervous ring, but probably without ganglia; but in all 

 other invertebrate animals, from the worms and moUusca to the crustaceans and in- 

 sects, the nervous system consists generally of a pair of ganglia above the esoph- 

 agus, called the brain, on the under side a second pair, and the four ganglia, 

 with the nerves and commissures connecting them, is often called the esophageal 

 ring, from which slender threads reach away to the various parts of the body. In 

 some forms the lower pair of ganglia are missing, and others have another pair, the 

 visceral ganglia, added. In the higher worms, Crustacea, and insects, there is a chain 

 of ganglia or brains which are ventral, and line the floor of the body cavity. In the 

 very highest invertebrates there is a mass of ganglia, as in the head of the cephalo- 

 pods. In the vertebrates the brain is more simple, consisting of a series of close- 

 set ganglia, forming a mass situated in a bony case, the skull, with the spinal cord 

 extending through the vertebra and having a definite relation to the sense organs, 

 and sending branches to all parts of the body. 



•'The tactile sense, or sense of touch, is common to all animals. It is the funda- 

 mental sense, of which all others are but modifications. The most conspicuous 

 sense organs are the eyes. A transparent spot on the front of some lower forms is 

 probably the simplest of all sense organs, and anticipates the eye of higher animals. 

 The simplest form of eyes is perhaps those of the sea anemone, in which there are. 

 besides pigment cells, refractive bodies, and from this true eyes develop as the scale 

 of life advances. In some worms true eyes appear — a projecting, spherical lens, 

 behind a vitreous body, retina, and optic nerve. In the crustaceans, the eyes assume 

 a quite definite place in the head, except in a few instances. In insects the eyes, 

 both simple and compound, are located definitely on the head. In the skulled verte- 

 brates, the eyes are of definite number, and in all types occupy a definite position in 

 the head. 



"The simplest kind of auditory organ is found in the jelly fishes, the first lower 

 form in which it appears. The otocysts, or simple ears, of the worms and moUusks 

 are minute and usually difficult to find, as is the auditory nerve leading to the nerve 

 centers. In the clams the ears are in the so-called foot; in the cuttle-fish and snails, 

 in the head close to the brain; in the shrimps and crabs, at the base of the mandibles; 

 in a few other crustaceans, at the base of the tail. In the insects there is a real tym- 

 panum cavity — a sac with a ganglionic cell within, but the position is very vari- 

 able. In the locusts, the ears are at the base of the abdomen; in the katydids and 

 crickets, in the fore tibia; in the butterflies, probably in the antenna?, etc. In the 

 vertebrata the ears are two in number, and are definitely situated on the sides oi" 

 the head. The sense of smell is obscurely indicated by special sense organs in the 

 invertebrate animals, nasal organs, as such, being characteristic only of the skulled 

 vertebrates. The organ of taste seems to be specially differentiated only in the ver- 

 tebrates, so far as we can tell." 



Our field is thus reduced to the vertebrates, for the sense organs are so scattered 

 throughout the body in the invertebrates that there is really no such part as the face> 

 in that class, as understood when speaking of the vertebrates. It is in this latter 

 class only that this part becomes apparent as the seat of four of the special senses. 

 How, then, does the face originate and develop in the vertebrata? 



In the vertebrates ( Mr. Wright, op. ciL), " all the higher sense organs may be re- 

 garded as differentiated parts of the skin, the nerves of which have become greatly 

 specialized, and have thus acquired a more marked individuality than the other sen* 



