Sentence:  Inside , carefully packed in straw , were six eggs , but the eye of a poultry psychologist was required to detect what scientifically valuable specimentalia lay inside ; to Alex they were merely six not unusual hens ' <WSD>eggs</WSD> . 
Meaning of the word marked with <WSD> tags:  animal reproductive body consisting of an ovum or embryo together with nutritive and protective envelopes; especially the thin-shelled reproductive body laid by e.g. female birds