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Fig. 15.—Section of Scolopendrella immaculata: œ, œsophagus; oe. v, œsophageal valve entering the mid-intestine (“stomach”); i, intestine; r, rectum; br, brain; ns, abdominal chain of ganglia; ovd, oviduct; ov, ovary; s. gl, silk-gland, and op, its outer opening in cercus, ur. t, urinary tube; cg, coxal glands or blood-gills.—Author del.

In 1888 Grassi expressed his view as to the position of the Symphyla, stating that it should not be included in the Thysanura, since it evidently has myriopod characters; these being the supraspinal vessel, the ventral position of the genital glands; the situation of the genital opening in the fourth segment of the trunk, its ganglionic chain being like that of diplopods, its having limbs on all the segments, etc. On the other hand, Grassi has with much detail indicated the points of resemblance to the Thysanura. The principal ones are the thin integument, the want of sympathetic ganglia, the presence of a pair of cephalic stigmata, like that said to occur in certain Collembola, and in the embryo of Apis; two endoskeletal processes situated near the ventral fascia of the head; the epicranial suture also occurring in Thysanura, Collembola, Orthoptera, and other winged insects, and being absent in diplopods and chilopods. He also adds that the digestive canal both in Symphyla and Thysanura is divided into three portions; the malpighian tubes in Thysanura present very different conditions (there being none in Japyx), among which may be comprised those of Scolopendrella. In both groups there is a single pair of salivary glands. The cellular epithelium of the mid-intestine of Scolopendrella is of a single form as in Campodea and Japyx. The fat-body, dorsal vessel, with its valves and ostia, are alike in the two groups, as are the appendages of the end of the abdomen, the anal cerci (cercopoda) of Scolopendrella being the homologues of the multiarticulate appendages of Lepisma, etc., and of the forceps of Japyx. In those of Scolopendrella, we have found the large duct leading from the voluminous silk-gland, a single large sac extending forwards into the third segment from the end of the body (Fig. 15, s. gl). Other points of resemblance, all of which he enumerates, are the slight differences in the number of trunk-segments, the presence in the two groups of the abdominal “false-legs” (parapodia), the dorsal plate, and the mouth-parts. As regards the latter, Grassi affirms that there is a perfect parallelism between those of Scolopendrella and Thysanura. To this point we will return again in treating more especially of those of the Symphyla. Finally, Grassi concludes that there is “a great resemblance between the Thysanura and Scolopendrella.” He, however, believed that the Symphyla are the forerunners of the myriopods, and not of the insects, his genealogical tree representing the symphylan and thysanuran phyla as originating from the same point, this point also being, rather strangely, the point of origin of the arachnidan phylum.