122 
ME. H. N. MOSELEY ON THE ANATOMY AND 
is occupied by a fine network of connective tissue, the fine connective-tissue threads 
spring from masses exactly like these latter in appearance (Plate XIV. fig. 6, X). 
In Planarians the tissue-elements are morphologically in a rudimentary condition. 
In the lower Planarians there is a large amount of slimy protoplasmic undifferentiated, 
or sparingly differentiated, tissue ; in the Land-Planarians before us the differentiation 
is more perfect, but, at the same time, elements which probably perform very different 
functions are still, in many cases, hardly to be distinguished morphologically. The 
gland-cells, connective-tissue threads, and pigment-bodies are all of them more or less 
perfect differentiations of a primitive protoplasmic substance, which may be considered 
to represent the connective tissue of higher animals. Leuckart {loc. cit. p. 639) in the 
same manner says of the pigment-bodies of the medicinal leech that they belong to the 
connective-tissue elements, and resemble the rest of this substance found in the body, 
and(p. 640) refers to the great resemblance of the gland-cells in this animal to connec- 
tive tissue. In Bipalium and Rhynchodemus the differentiation of these several struc- 
tures has not gone so far as it has in the leech. The subcuticular glands of these 
Planarians probably represent the superficial glands of the leech called by Leydig 
“ einzellige Hautdrusen ” {loc. cit. Taf. i. fig. 6) ; whilst those situate deeper in the sub- 
stance of the body represent the deeper set of glands of that animal, which, singularly 
enough, are described by Leuceart as being more like transparent vesicles, and not so 
granulated in appearance as the superficial set, which exactly corresponds to what is 
found to be the case in Bipalium and Rhynchodemus. The resemblance in many points 
of structure between the leech and these Planarians is most striking ; and if sections of 
the skin treated in the same manner be examined side by side, the similarity in appear- 
ance is most remarkable, the pigment and glandular bodies being most alike, and the 
absence of “ Stabchen-Organe ” being the most striking difference. The glandular and 
connective-tissue masses appear to be represented in the lower Planarians by the struc- 
tures described and figured {loc. cit. 1, fig. 24) by Max Schultze as “ sehr zarte Fadchen 
mit Ausschwellungen ; ” but here there was yet no distinction between glandular and 
connective tissue. The “ Binde-Substance ” observed by Keferstein in Leptoplana is 
of the same nature ; and so are probably also"the “ plasmatische Kanale ” described and 
figured by Sommer and Laxdois {loc. cit. p. 10), which in the figure have the same 
granulated appearance as the glands of Rhynchodemus and Bipalium, and of which 
they state that their finest twigs form connexions with processes of connective-tissue- 
like bodies. As reference will not again be made specially to the connective tissue of 
the Planarians under consideration, it should be stated that an irregular network of slimy 
connective tissue is to be found all over the body between the muscles and around the 
various organs ; it is often seen to be connected with the large irregular masses which 
so closely resemble the glandular substance. 
Those portions of it which are specially developed to form capsules for the generative 
organs and the network in the water-vascular canals will be described with those organs. 
The basement membrane of the skin has already received description. The subcutaneous 
