If they are too short, then the membrane does not invaginate.
From the sciencedaily.com
The gonad wall starts to invaginate, ovarian tissue develops, and within a couple of weeks the testicular region has become small and non-functional.
From the independent.co.uk
For each cell, the scientists examined the variety in endocytosis activity, by which cells invaginate parts of its biological membrane and absorbs the surrounding medium.
From the sciencedaily.com
These interactions cause a region of the oral ectoderm to invaginate, or fold in on itself, and then detach itself to form a small sac called Rathke's pouch.
From the guardian.co.uk
More examples
Sheathe; "The chrysalis is invaginated"
Fold inwards; "some organs can invaginate"
(invagination) the condition of being folded inward or sheathed
(invagination) the folding in of an outer layer so as to form a pocket in the surface; "the invagination of the blastula"
Invagination to fold inward or to sheath. In biology, this can refer to a number of processes.
To fold up or enclose into a sheath-like or pouch-like structure, either naturally or as part of a surgical procedure; To turn or fold inwardly; Infolding to create a hollow space where none had existed, as with a gastrula forming from a blastula
(invagination) The process where an anatomical part invaginates upon itself or into another structure; One of the methods by which the various germinal layers of the ovum are differentiated
(invaginated) for scolex, being withdrawn within the body of the metacestode by turning outside-in, in a way which renders its apex the bottom of a cavity while the external walls of the scolex become the internal walls of the same cavity. ...
(invagination) a stage in embryonic development where a cell layer buckles inward