SLIME BUDS. 117 



or by the same nerves that supply the adjacent gustatory organs. Those that are 

 scattered over the general surface of the body are supplied by branches from a sub- 

 cutaneous plexus, formed by the ramifications of the general cutaneous branches 

 of the haemal nerves. In the appendages, the subdermal plexus arises from the 

 general cutaneous branches of the neural nerves. 



4. Structure. Slime buds are found in many Crustacea and arachnids, and, 

 although but little is known about them, they appear to have a similar structure 

 to those in Limulus. 



The slime buds differ in appearance in different regions, and apparently at 

 different times. They are generally spherical or oval, with a small central space 



FIG. 86. Anterior, or outer, surface of the branchial appendage of a young Limulus, two inches long. A, a 

 portion of the subdermal plexus of nerve fibers, with clusters of bipolar sense cells whose outer ends terminate in 

 minute chitenous spikes; A, one of the sense buds, more highly magnified, with its chitenous tubule, ch.t., that 

 conveys the terminal fibers to the surface; B, two apparently isolated multipolar ganglion cells, lying just below, 

 or in, the surface ectoderm of the branchial appendage; C, four multipolar ganglion cells from the same region. 

 Methylene blue. 



from which a chitenous tubule leads to the exterior. (Fig. 88.) This tubule 

 may or may not be convoluted near its origin, but it generally terminates in a 

 straight delicate tubule that cannot be distinguished from those covering the 

 outer ends of the gustatory and temperature-cells. All the tubules aie shed with 

 the old shell at ecdysis. They may be seen protruding a considerable distance from 

 the inner surface of the cast off shell that have been cleaned with boiling potash. 

 The slime buds contain at least two different kinds of cells, namely, true 

 slime cells, which may constitute the greater part of the organ, and one or more 

 sensory cells. The slime cells vary greatly in appearance. In the typical ol- 

 factory and mandibular slime buds, they are irregularly conical or cylindrical, 

 their walls are sharply defined, and they contain, at their pointed central ends, a 

 mass of refractive colorless spherules. The enlarged peripheral ends of the cells, 



