It is also a remarkable fact that hybrids raised from reciprocal crosses, though of course compounded of the very same two species, the one species having first been used as the father and then as the mother, though they rarely differ in external characters, yet generally differ in fertility in a small, and occasionally in a high degree.
Halaber egitate azpimarragarria da elkarrekiko gurutzaketaz sorturiko hibridoek, nahiz eta, jakina, bi espezie berek osatuak diren, espezie bakoitza lehenik aita izanik eta gero ama izanik edo alderantziz erabili delako, kanpo-ezaugarrietan alderik inoiz gutxitan izaten duten arren, ugalkortasunean eskuarki alde apur bat, eta noizbehinka handia, izaten dutela.