Translation of Lang's original description as Aceros inconspicuus
provided by EOL authors
21. Genus. Aceros nov. gen. Body smooth. Mouth immediately beneath the brain. Cylindrical phyarnx. Major intestine with about five pairs of intestinal branches. Male opening very close behind the mouth. Male copulatory apparatus under the pharyngeal pocket; the female system with its opening tightly behind that. A few uterus glands. Very few eyes (on each side three) in the cerebral region. Very few eyes also in lateral groups on the anterior body edge, in the sites where tentacles occur in related genera, which in this genus are entirely absent. Aceros inconspicuus nov. spec. Table 2, Figure 9 This unseemly animal, which in its outstretched condition is not over 3 mm long and 1.3 mm wide, has an elongate oval aspect, gently rounded at front and back. It lacks any hint of tentcles. The body is slightly transparent, whitish on a black background. On the back side [dorsal] show small white flecks and points throughout, which originate for the most part from the gleaming ovaries. Towards the center the body becomes more intensely white and opaque. The dorsal side is clothed evenly throughout with small black flecks, smaller than the white points, and denser. They originate from small aggregations of finely granular pigment, which are situated immediately beneath the basal membrane. The branched, non-anastamosing yellowish or whitish intestinal branches shine through only dimly. The inconspicuous brain region lies not far behind the anterior end. In it lay three pairs of eyes, which show exactly the same order as the three anterior pairs of cerebral eyes in Stylostomum variabile. The two forwardmost, smallest eyes are most widely spaced from each other; they lay deeper in the parenchyma on the frontal and lateral edges of the brain. The four back [eyes] lie toward the midline, somewhat more directly above the brain. The two on the same side are close to one another, the frontal [of the back two] somewhat nearer to the median line than the back pair. At the anterior end of the body a group of four small eyes lie right and left of the midline, which are decidedly more on the belly side [ventral] than the backside [dorsal]. They lay exactly in the precise spots where the tentacular eyes of Stylostomum occur. By virtue of the positions of the eyes the living animal reminds one strongly of the more advanced stages of the Mueller’s larva. I would actually like to consider this species as a sexually mature form of a juvenile euryleptid. The belly side [ventral] of the animal is dirty white, and the pharynx and sexual apparatus shine indistinctly through. The mouth lies towards the end of the first quarter of the body, the male sexual opening very near behind the mouth. The female opening occurs somewhat to the front of midbody, the adhesive sucker, somewhat behind. Except that the mouth opening is split from the sexual opening and that the frontal-median intestinal branch is also in the region of the pharynx, the anatomy of Aceros agrees entirely with that of Stylostomum, and especially in the construction of the pharynx, the gastrovascular system, and both sexual systems. The fundamentals of the anatomy have been elucidated on Table 24, Figure 8, which depicts a median longitudinal section through the body. The little animal can hold itself very tightly to the substrate below with the help of its adhesive sucker. If it is left alone, so that it is almost round, only when crawling does it stretch itself to its full length. It does not have the ability to swim freely in the water. Locality: I found once a number of exemplars between Posidonia roots which were broken off from Posilipo; I collected further individuals from algae in Castello dell’uovo and Carmine.
