What is the shape of the sinus venosus?

Which of the following structures does the given figure represent?

Identify ‘3’ in the pathway of food ingested by frog.

What does the question mark represent in the following figure?

At which of these segments does the nerve cord of the earthworm divide into two parts?

Where are the calciferous glands of the earthworm present?

The epidermal pits in the middle of each segment of the earthworm contains _____

Which of the following represent the intercellular matrix of a bone?