Final answer:
Peripatus is seen as a connecting link between Arthropoda and Annelida as it shares features with both, such as segmentation and multiple pairs of legs from arthropods, and a soft body like annelids. Their unique reproductive behaviors further suggest a blend of complexities from both phyla, even though molecular evidence places them in separate evolutionary clades.
Step-by-step explanation:
Peripatus is considered a connecting link between the phyla Arthropoda and Annelida due to its combination of characteristics from both groups. These caterpillar-like animals exhibit features like a segmented body and multiple pairs of legs characteristic of arthropods, while also having a soft, non-chitinized body similar to annelids. More specifically, the presence of a high number of legs and segmentation align Peripatus with arthropods, but the absence of a hard, chitinous exoskeleton hints at annelidan features.
The segmentation seen in Peripatus resembles that of both annelid worms, where the body is divided into a series of ring-like segments, and arthropods, which also have segmented bodies but with jointed appendages. The way Peripatus practices reproduction is another point of interest, highlighting both primitive and complex reproductive behaviors which could suggest transitional evolutionary steps between the two phyla. Although Peripatus shares morphological similarities with these groups, molecular evidence suggests that arthropods and annelids belong to separate clades: Ecdysozoa and Lophotrochozoa, respectively.