Evolution of life Philadelphia, 1873, This illustration depicts a series of four skulls displayed in a sequential arrangement. The leftmost skull is small and resembles that of a smaller creature, while the subsequent skulls increase in size, showcasing a gradual transition to a larger, more human-like skull on the far right. Each skull is labeled with a numerical designation: 187, 138, 199, and 200. The varying shapes and dimensions highlight differences in species or developmental stages, providing insights into anatomical evolution or comparative anatomy studies. The overall composition emphasizes the progression and diversification of skeletal features across different entities.