428 



SCIENCE. 



[N. S. Vol. V. No. 115. 



organs in the appendages of the body are 

 like those over the sense organs of Lum- 

 bricus. Over the body itself each cuticular 

 marking is concave on the exterior and the 

 very thick cuticula encloses beneath each 

 marking an ovoid cavity through which pass 

 the outer ends of the sensory cells. Each 

 sensory cell usually bears several sensory 

 hairs, and these hairs cannot be retracted 

 normally as supposed by Retzius. 



In the gill lobes of the parapodia, the 

 base of the palps, the prostomium and 

 several anterior metameres is found a 

 second kind of sense organ, apparently a 

 light-perceiving organ, not previously de- 

 scribed. ^ 



In the center of each organ is a slender, 

 flexible tube, open to the exterior and con- 

 tinuous vpith the cuticula. Around this 

 tube the club-shaped peripheral ends of 100 

 or more bi- or multipolar nerve cells are ar- 

 ranged in a spiral of from 8 to 1-1 turns. The 

 bodies of these cells are irregularly grouped- 

 in or beneath the base of the epidermis ; the 

 central nerve fibre passes to the central 

 nervous system ; the peripheral fibre is at 

 first slender, but ends in the club-shaped 

 enlargement mentioned above. The tip of 

 this enlargement, and sometimes the entire 

 enlargement itself, is filled with a clear, 

 highly refractive, lens-like substance. 



The central fibres fi'om both diffuse and 

 light- perceiving organs end in apparent nerve 

 baskets around the ganglion cells of the 

 central nervous system. 



Beside the four eyes and the two pairs of 

 sense organs of unknown function described 

 by Retzius, the prostomium contains a third 

 pair of organs near the anterior pair of 

 Retzius. The groups of ganglion cells de- 

 scribed by Retzius near the anterior eyes 

 are not, as that author supposed probable, 

 concerned with the innervation of the ej'es ; 

 the preparations from which this studj^ was 

 made show plainly the nerve bundles pass- 

 ing from the eyes to the brain. 



Epidermal Sense Organs in Certain Polychcetes, 



Margaret Lewis. 



The epidermal sense organs were studied 

 in two members of the annelid family of the 

 Maldaniae, both by means of ordinary 

 methods and by the use of methylin blue. 

 The following are the chief conclusions : 



1. That multicellular sense organs are 

 present throughout the integument of the 

 two polychaste annelids Glymenella torquata 

 and Clymene longa. 



2. That the cells of these sense organs 

 are spindle-shaped, bipolar nerve cells. 



3. That the individual cells making up a 

 sense organ show great variation in the dis- 

 tance of the enlargement containing the 

 nucleus from the cuticula. This enlarge- 

 ment may be close to the cuticula, at half 

 the height of the epidermis or sunk to the 

 base of the epidermis. 



4. That the cells of the sense organs pos- 

 sess at their peripheral ends sensory hairs. 



5. That from the deep end of each cell 

 proceeds one process which turns at an an- 

 gle beneath the epidermis toward the cen- 

 tral nervous system. 



6. That in many respects the sensory 

 cells of these epidermal sense organs show 

 a striking resemblance to the epidermal 

 sense cells which Retzius describes for 

 Nereis ; the chief difference being that Ret- 

 zius found only isolated sense cells in the epi- 

 dermis of Nereis, whereas in these Malda- 

 nids these sense cells without exception are 

 grouped into definite sense organs. 



Tlie Eyes of Limax maximus. A. P. Hench- 

 man. 



The ej^e consists of six pai-ts: (1) Optic 

 ganglion, (2) Sclerotic capsule, (3) Retina, 

 (4) Vitreous humor, (5) Lens, and (6) 

 Corneal layer. The optic ganglion is a 

 funnel-shaped enlargement of the optic 

 nerve, containing oval nuclei. The scler- 

 otic capsule is a thin, firm layer of con- 

 nective tissue, containing at intervals oval 



