	Nevertheless, dissection is required to distinguish "D. invadens" reliably from "D. laeve" and from various similar "Deroceras" species occurring in Europe, such as "Deroceras sturanyi", the true "Deroceras panormitanum", and "Deroceras golcheri". Reise et al. (2011) discuss and figure the most critical anatomical characters. In most populations of "D. invadens", the proximal penis has two side pockets (the penial caecum and penial lobe); these have roughly equal widths and both have rounded, stout ends. A prominent appending penial gland with 3–7 branches attaches between the caecum and lobe on the dorsal side; these branches are less knobbly in outline than those of "D. panormitanum". The penial retractor muscle attaches between the caecum and lobe on the ventral side. The intestinal caecum is either absent or represented merely by a widening of the rectum. Barker (1999) and Sirgel (1973) detail various other aspects of the anatomy.