20 PEOF. M. M. HAETOG ON THE 



water, and leave them exposed to sunlight for a day or two, transfer through the alcohols 

 to oil of cloves, and then in some dissections the areas will be found especially visible on 

 the appendages (PL I. fig. 9). They are very large for the size of the animal. 



I would note here that while the cuticle is fairly impervious to stains, it is very readily 

 traversed by even dilute acids (as well as gold and silver solutions), so that it probably 

 offers no great impediment to cutaneous respiration. That the hypoderm stains so badly, 

 as a rule, is comparable to the difficulty with which the underside of a section or soft 

 animal lying on glass takes its proper coloration. 



A tabular list of the various forms of hair has been given above. In connection 

 with the skin the following points about moulting are of interest. Before each moult a 

 collection of connective-tissue cells is seen below the integument, which only disappear 

 gradually after the moult. The hypoderm is withdrawn from the old hairs ; and the new 

 hairs (even the long caudal spines) are inverted into the body to be everted at the moult. 

 At each moult an increase takes place in the number of segments and the joints of the 

 appendages, especially the antennules; when the full number is reached no further 

 moult takes place. It is probable that even the finest setse and teeth contain a process of 

 hypoderm, or are at least hollow, for the cuticle of the plume or saw is traversed, in 

 silver-nitrate specimens, by a dark line at the base of each seta. 



Pore-canals and Glands. — These occur regularly in certain parts. They are oval, much 

 vacuolated cells, with a spheroidal nucleus toward the proximal end, in all cases inclined 

 obliquely towards the surface, and open distally in a minute slit-shaped pore in the cuticle. 

 Each receives at its base a nerve-fibre, which passes just before through a bipolar gang- 

 lion-cell. In some cases I observed in a large vacuole, adjacent if not belonging to a 

 pore-canal, irregular concretions. These I found at one time constant at tbe base of the 

 5th thoracic limb in a collection of males of this species, and regarded as auditory organs*. 



Tbe distribution of some of the most obvious is as follows: — 



Trunk : 5th thoracic segment, one at base of each appendage, innervated from ganglion 

 in 4th segment ; 6th thoracic segment, one pair ventro-lateral, internal to genital aperture 

 (innervated from enlargement on ventral cord close to its bifurcation) ; 1st, 2nd, 3rd, 4th 

 abdominal segments each one ventral pair, and (except the fourth) one lateral pair. 



Furca : one pair on outer side, opening about one third the way down, and at least 

 two near distal end, on ventral side. 



Swimming-feet : one at the base of each " saw " on the exopodite, opening distally and 

 anterior to it, and one at the base of each corresponding tooth or plume on the endopodite 

 (PI. I. fig. 9,2>c). 



Whether these organs are to be regarded as rather nervous or excretory is uncertain. 

 Similar " glands " are found in many groups of Vermes as well as in Arthropoda. 



CCELOM AND ITS CONNECTIVE AND MUSCULAR TISSUES. 



The connective tissues of the body form irregular lacunar trabecule, with nuclei 

 scattered through them. They are so distributed as to form mesenteries to the alimentary 

 canal and reproductive organs, and in some cases form a sarcolemma to the muscles, 



* See also below, in the account of the nervous system. 



