In the case of my example at b. Deductive Demonstration , the term ( = middle term) which indicates the cause is : 'animals'. Because sponges are animals they are cellular. To answer the question as to the whatness of 'cellular' we thus refer to a higher level, namely 'animals'. The 'nature' of (that what is signified by the term) 'animals' constitutes (that what is signified by the term) 'cellularity'. By referring to 'animals' we know what 'cellularity' is, and if not, then we must refer further (up).
'Animals' is a part of the definitio quid rei of 'cellularity'. That is, 'animals' is comprised in the extension (range) of the concept 'cellularity'. 'Animals' is in fact only then really a cause if cellularity would be limited to animals.